JP6725212B2 - CdTe compound semiconductor and radiation detection element using the same - Google Patents
CdTe compound semiconductor and radiation detection element using the same Download PDFInfo
- Publication number
- JP6725212B2 JP6725212B2 JP2015085337A JP2015085337A JP6725212B2 JP 6725212 B2 JP6725212 B2 JP 6725212B2 JP 2015085337 A JP2015085337 A JP 2015085337A JP 2015085337 A JP2015085337 A JP 2015085337A JP 6725212 B2 JP6725212 B2 JP 6725212B2
- Authority
- JP
- Japan
- Prior art keywords
- cdte
- concentration
- holes
- compound semiconductor
- boron
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 239000004065 semiconductor Substances 0.000 title claims description 81
- 230000005855 radiation Effects 0.000 title claims description 37
- 150000001875 compounds Chemical class 0.000 title claims description 25
- 238000001514 detection method Methods 0.000 title claims description 25
- 229910004613 CdTe Inorganic materials 0.000 title claims 11
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 74
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 46
- 229910052796 boron Inorganic materials 0.000 claims description 46
- 229910052757 nitrogen Inorganic materials 0.000 claims description 37
- 239000000758 substrate Substances 0.000 claims description 29
- 229910052738 indium Inorganic materials 0.000 claims description 3
- 229910052697 platinum Inorganic materials 0.000 claims description 3
- MARUHZGHZWCEQU-UHFFFAOYSA-N 5-phenyl-2h-tetrazole Chemical compound C1=CC=CC=C1C1=NNN=N1 MARUHZGHZWCEQU-UHFFFAOYSA-N 0.000 description 47
- 239000013078 crystal Substances 0.000 description 32
- 239000000463 material Substances 0.000 description 28
- 239000012535 impurity Substances 0.000 description 26
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 19
- 238000010438 heat treatment Methods 0.000 description 19
- 239000001301 oxygen Substances 0.000 description 19
- 229910052760 oxygen Inorganic materials 0.000 description 19
- -1 CdTe compound Chemical class 0.000 description 15
- 229910052799 carbon Inorganic materials 0.000 description 13
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 12
- 238000000034 method Methods 0.000 description 12
- 239000000969 carrier Substances 0.000 description 11
- 239000010453 quartz Substances 0.000 description 11
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 11
- 239000003708 ampul Substances 0.000 description 9
- 230000000052 comparative effect Effects 0.000 description 9
- 239000000203 mixture Substances 0.000 description 9
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 7
- 229910002090 carbon oxide Inorganic materials 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 7
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Substances [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 7
- 229910001868 water Inorganic materials 0.000 description 7
- PZNSFCLAULLKQX-UHFFFAOYSA-N Boron nitride Chemical compound N#B PZNSFCLAULLKQX-UHFFFAOYSA-N 0.000 description 6
- 230000005684 electric field Effects 0.000 description 6
- 230000007423 decrease Effects 0.000 description 5
- 238000006243 chemical reaction Methods 0.000 description 4
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 3
- CEKJAYFBQARQNG-UHFFFAOYSA-N cadmium zinc Chemical compound [Zn].[Cd] CEKJAYFBQARQNG-UHFFFAOYSA-N 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000007711 solidification Methods 0.000 description 3
- 230000008023 solidification Effects 0.000 description 3
- 239000011701 zinc Substances 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 229910052582 BN Inorganic materials 0.000 description 2
- CPELXLSAUQHCOX-UHFFFAOYSA-N Hydrogen bromide Chemical compound Br CPELXLSAUQHCOX-UHFFFAOYSA-N 0.000 description 2
- LXQXZNRPTYVCNG-YPZZEJLDSA-N americium-241 Chemical compound [241Am] LXQXZNRPTYVCNG-YPZZEJLDSA-N 0.000 description 2
- 230000008901 benefit Effects 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000005498 polishing Methods 0.000 description 2
- 230000006798 recombination Effects 0.000 description 2
- 238000005215 recombination Methods 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- 229910052714 tellurium Inorganic materials 0.000 description 2
- PORWMNRCUJJQNO-UHFFFAOYSA-N tellurium atom Chemical compound [Te] PORWMNRCUJJQNO-UHFFFAOYSA-N 0.000 description 2
- WKBOTKDWSSQWDR-UHFFFAOYSA-N Bromine atom Chemical compound [Br] WKBOTKDWSSQWDR-UHFFFAOYSA-N 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- GDTBXPJZTBHREO-UHFFFAOYSA-N bromine Substances BrBr GDTBXPJZTBHREO-UHFFFAOYSA-N 0.000 description 1
- 229910052794 bromium Inorganic materials 0.000 description 1
- UHYPYGJEEGLRJD-UHFFFAOYSA-N cadmium(2+);selenium(2-) Chemical compound [Se-2].[Cd+2] UHYPYGJEEGLRJD-UHFFFAOYSA-N 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000007772 electroless plating Methods 0.000 description 1
- 238000005530 etching Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 230000008014 freezing Effects 0.000 description 1
- 238000007710 freezing Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000001036 glow-discharge mass spectrometry Methods 0.000 description 1
- 229910000042 hydrogen bromide Inorganic materials 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical group [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 229910021642 ultra pure water Inorganic materials 0.000 description 1
- 239000012498 ultrapure water Substances 0.000 description 1
- 238000004506 ultrasonic cleaning Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- 230000003442 weekly effect Effects 0.000 description 1
- NWJUKFMMXJODIL-UHFFFAOYSA-N zinc cadmium(2+) selenium(2-) Chemical compound [Zn+2].[Se-2].[Se-2].[Cd+2] NWJUKFMMXJODIL-UHFFFAOYSA-N 0.000 description 1
Images
Landscapes
- Light Receiving Elements (AREA)
- Measurement Of Radiation (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
Description
本発明は、ＣｄＴｅ系化合物半導体及びそれを用いた放射線検出素子に関する。 The present invention relates to a CdTe compound semiconductor and a radiation detection element using the same.
従来より、放射線検出素子用途で高効率、高分解能、小型化に優れた直接変換型化合物半導体の開発が進められている。その中でＩＩ−ＶＩ族化合物半導体であるテルル化カドミウム（ＣｄＴｅ）、セレンテルル化カドミウム（ＣｄＳｅＴｅ）、テルル化亜鉛カドミウム（ＣｄＺｎＴｅ）、セレンテルル化亜鉛カドミウム（ＣｄＺｎＳｅＴｅ）などのＣｄＴｅ系化合物半導体は、近年、放射線検出素子用途の有力な材料として注目されている。これらは他の半導体に比べ、原子番号が比較的大きいことから放射線の吸収率が高く検出効率が高い、バンドギャップエネルギーが大きいので熱による漏れ電流の影響が少なく冷却装置が不要（室温で動作可能）という利点がある。 2. Description of the Related Art Conventionally, direct conversion type compound semiconductors having high efficiency, high resolution, and excellent miniaturization for use in radiation detection elements have been developed. Among them, CdTe compound semiconductors such as cadmium telluride (CdTe), cadmium telluride (CdSeTe), zinc cadmium telluride (CdZnTe), zinc cadmium telluride (CdZnSeTe), which are II-VI group compound semiconductors, have recently been used. It has attracted attention as a powerful material for use in radiation detection elements. Compared to other semiconductors, these have a relatively large atomic number, so the radiation absorption rate is high and the detection efficiency is high. The bandgap energy is large, so there is little effect of leakage current due to heat and no cooling device is required (it can be operated at room temperature). ) Has the advantage.
こうした放射線検出用直接変換型半導体において、放射線検出特性の良し悪しを決める半導体の重要なパラメータにキャリアの移動度μとキャリア寿命τの積μτが挙げられる。直接変換型半導体を用いた放射線検出器は、半導体の対向する２面に電極を形成し、電極を介して電場が印加された状態の半導体内に放射線が入射することで発生するキャリア（電子・正孔）を電極を介して電気信号の形で取り出すことによって放射線が入ったことを感知する。すなわち、電場が印加された状態の半導体内では、放射線を吸収して発生したキャリア（電子・正孔）が、印加された電場に沿ってそれぞれ相反する電位の方向に進み、最終的に電極まで到達する。電極に到達したキャリア（電子または正孔）が電気信号の形で取り出されるため、放射線が入ったことを電気信号の形で感知できるというのが、直接変換型半導体を用いた放射線検出素子の原理である。 In such a direct conversion semiconductor for radiation detection, an important parameter of the semiconductor that determines whether the radiation detection characteristics are good or bad is the product μτ of carrier mobility μ and carrier lifetime τ. A radiation detector using a direct conversion type semiconductor has electrodes formed on two opposite surfaces of the semiconductor, and carriers (electrons, electrons, etc.) generated when radiation enters the semiconductor in a state where an electric field is applied through the electrodes. The fact that the radiation has entered is detected by taking out (holes) in the form of an electric signal through the electrodes. In other words, in a semiconductor to which an electric field is applied, carriers (electrons/holes) generated by absorbing radiation travel in opposite potential directions along the applied electric field and finally reach the electrodes. To reach. Since the carriers (electrons or holes) that reach the electrodes are extracted in the form of an electric signal, the fact that radiation has entered can be detected in the form of an electric signal is the principle of a radiation detection element using a direct conversion semiconductor. Is.
この際、半導体のキャリア移動度μが大きい程、半導体内をキャリアは早く移動し、電極まで到達し易い。また、キャリア寿命τが大きい程、キャリアは再結合で失われず長寿命なため電極まで到達し易くなる。従って、この二つの積μτは放射線入射で発生したキャリアが途中で失われずに電極まで届く尺度を表し、この値が大きい程、放射線検出特性に優れている。また、キャリアの種類（電子・正孔）によって、異なるμτ値を有している。正孔の移動度μは、電子の移動度μに比べて小さく、正孔における積μτ（ｈ）（正孔のμτ（ｈ））は電子における積μτ（ｅ）（電子のμτ（ｅ））より１〜２桁低い値になることが多く、放射線検出特性を下げる原因となっている。そこで、正孔のμτ（ｈ）を高めることが放射線検出特性の向上に繋がる。 At this time, the higher the carrier mobility μ of the semiconductor, the faster the carriers move in the semiconductor and the easier they reach the electrodes. Further, as the carrier life τ is longer, carriers are not lost by recombination and have a longer life, so that they easily reach the electrode. Therefore, these two products μτ represent a scale by which carriers generated by radiation incidence reach the electrode without being lost in the middle. The larger this value, the better the radiation detection characteristics. Further, it has different μτ values depending on the type of carriers (electrons/holes). The mobility μ of holes is smaller than the mobility μ of electrons, and the product μτ(h) of holes (μτ(h) of holes) is the product μτ(e) of electrons (μτ(e) of electrons). In many cases, the value is lower by 1 to 2 digits than that of the above), which is a cause of lowering the radiation detection characteristics. Therefore, increasing μτ(h) of holes leads to improvement of radiation detection characteristics.
また、例えば、組成が同じＣｄＴｅ化合物半導体を用いて放射線検出器を作製した際、同じ条件で作製した電極を用いても放射線の検出特性にばらつきが生じていた。実際に正孔のμτ（ｈ）値を測定すると、組成が同じＣｄＴｅ系化合物半導体であっても、製造の度毎に、１０−５〜１０−６ｃｍ２／Ｖ台まで大きくばらついていた。したがって、正孔のμτ（ｈ）値をできる限り高い値とし、そのばらつきを抑えることで、再現性よく高いμτ（ｈ）を有するＣｄＴｅ系化合物半導体基板を得る技術が求められてきた。 Further, for example, when a radiation detector is manufactured using CdTe compound semiconductors having the same composition, variations in radiation detection characteristics occur even if electrodes manufactured under the same conditions are used. When the μτ(h) value of holes was actually measured, even in the case of CdTe compound semiconductors having the same composition, the values were largely varied up to the level of 10 −5 to 10 −6 cm 2 /V for each production. Therefore, there has been a demand for a technique for obtaining a CdTe-based compound semiconductor substrate having high μτ(h) with high reproducibility by making the μτ(h) value of holes as high as possible and suppressing the variation.
非特許文献１には、正孔の移動度μは電子の移動度μに比べて小さく、正孔のμτ（ｈ）は電子のμτ（ｅ）に比べて値が小さく、放射線検出器の出力が放射線の入射方向によって変化する問題点を指摘している。この問題を解決するために、電極に用いる金属の組成を調整してキャリアの収集効率を改善することが記載されている。 In Non-Patent Document 1, the mobility μ of holes is smaller than the mobility μ of electrons, μτ(h) of holes is smaller than μτ(e) of electrons, and the output of the radiation detector is Point out the problem that changes depending on the incident direction of radiation. In order to solve this problem, it is described that the composition of the metal used for the electrode is adjusted to improve the carrier collection efficiency.
しかしながら、正孔を電極から取り出す効率を高め、放射線検出素子としての機能向上を図ることができるとしても、正孔のμτ（ｈ）値自体の改善には繋がっていない。また、組成が同じＣｄＴｅ化合物半導体に同じ条件で作製した電極を用いても放射線の検出特性にばらつきが生じていたという問題、すなわち、組成が同じＣｄＴｅ系化合物半導体であっても個体によって正孔のμτ（ｈ）値が、製造の度毎に、１０−５〜１０−６ｃｍ２／Ｖ台まで大きくばらつく問題を解決するものでもない。 However, even if it is possible to improve the efficiency of extracting holes from the electrodes and improve the function of the radiation detecting element, this does not lead to an improvement in the μτ(h) value itself of the holes. Further, even if the electrodes prepared under the same conditions are used for the CdTe compound semiconductors having the same composition, the radiation detection characteristic varies, that is, even if the CdTe compound semiconductors having the same composition have different holes depending on the individual. It does not solve the problem that the μτ(h) value greatly varies up to the level of 10 −5 to 10 −6 cm 2 /V each time it is manufactured.
本発明の課題は、組成が同じＣｄＴｅ系化合物半導体の正孔のμτ（ｈ）値をできる限り高い値とし、あわせてそのばらつきが抑えられたＣｄＴｅ系化合物半導体を提供することである。さらに、そのようなＣｄＴｅ系化合物半導体を用いた放射線検出素子を提供することである。 It is an object of the present invention to provide a CdTe-based compound semiconductor in which the μτ(h) value of holes in CdTe-based compound semiconductors having the same composition is set as high as possible and the variation thereof is suppressed. Furthermore, it is to provide a radiation detection element using such a CdTe compound semiconductor.
我々はこうした問題点の解決のため、鋭意研究開発を進めたところ、正孔のμτ（ｈ）値（移動度−寿命積μτ（ｈ））がＣｄＴｅ系半導体に含まれる不純物のうちボロン（Ｂ）、炭素（Ｃ）、窒素（Ｎ）、及び酸素（Ｏ）の濃度に強く依存していることを見出した。傾向として、ボロン（Ｂ）、炭素（Ｃ）、窒素（Ｎ）、及び酸素（Ｏ）の濃度が少ない程、正孔のμτ（ｈ）値が高いことがわかった。特に、ボロン（Ｂ）が低い場合に、正孔のμτ（ｈ）が高くなりやすく、さらに、正孔のμτ（ｈ）値はボロン（Ｂ）及び窒素（Ｎ）の合計の濃度に強く依存していることが分かった。より具体的には、（１）ボロン（Ｂ）濃度が高い場合には、窒素（Ｎ）濃度が極めて低い場合でも、正孔のμτ（ｈ）が小さくなる（比較例２）。（２）ボロン（Ｂ）の濃度及び窒素（Ｎ）濃度のいずれも低い場合には安定して正孔のμτ（ｈ）が大きな値を得る（実施例１、２）ことができ、（３）炉材の熱処理時間を長くすることによって、該炉材を使用して育成したＣｄＴｅ系結晶中の酸素（Ｏ）濃度が減少する傾向を見出し、本発明に至った。これらの不純物濃度を抑えることで正孔のμτ（ｈ）値を高めるとともに、組成が同じＣｄＴｅ系化合物半導体における個体間の正孔のμτ（ｈ）値のばらつきを改善させることに成功した。 As a result of intensive research and development for solving these problems, we have found that the μτ(h) value of holes (mobility-lifetime product μτ(h)) is boron (B) among impurities contained in CdTe semiconductors. ), carbon (C), nitrogen (N), and oxygen (O). As a tendency, it was found that the smaller the concentrations of boron (B), carbon (C), nitrogen (N), and oxygen (O), the higher the μτ(h) value of holes. In particular, when boron (B) is low, μτ(h) of holes tends to be high, and the μτ(h) value of holes strongly depends on the total concentration of boron (B) and nitrogen (N). I found out that More specifically, (1) When the boron (B) concentration is high, μτ(h) of holes is small even when the nitrogen (N) concentration is extremely low (Comparative Example 2). (2) When both the boron (B) concentration and the nitrogen (N) concentration are low, a large value of μτ(h) of holes can be stably obtained (Examples 1 and 2), and (3) ) By prolonging the heat treatment time of the furnace material, it was found that the oxygen (O) concentration in the CdTe-based crystal grown using the furnace material tends to decrease, and the present invention has been completed. By suppressing the concentration of these impurities, we succeeded in increasing the μτ(h) value of holes and improving the variation of the μτ(h) value of holes in individual CdTe compound semiconductors having the same composition.
ＣｄＴｅ系結晶（結晶には、単結晶及び多結晶を含む。）の育成工程において、混入している酸素（Ｏ）はそれ自体、ＣｄＴｅ系半導体内でμτ低下に関与する等電位トラップ準位を形成する。さらに、炉材に付着した水分の酸素（Ｏ）成分は炉材に使われる窒化ほう素材（ＢＮやｐＢＮ）から、窒素（Ｎ）、ボロン（Ｂ）をＮＯｘ、ＢＯｘの形で炉材から解離させ、結晶内に取り込ませてしまう性質があると考えられる。加えて、同じく炉材に使われる石英は炭素酸化物（ＣＯｘ）を取り込む性質があり、これも汚染源となる。そのため、まずはＣｄＴｅ系半導体の結晶製造装置内に含まれる酸素（Ｏ）濃度及び炭素酸化物（ＣＯｘ）濃度を下げることで、ＣｄＴｅ系半導体結晶中の不純物濃度を下げることが可能となるかを試みた。 In the growing process of a CdTe-based crystal (the crystal includes a single crystal and a polycrystal), the mixed oxygen (O) itself has an equipotential trap level involved in μτ reduction in the CdTe-based semiconductor. Form. Furthermore, the oxygen (O) component of the water adhering to the furnace material is dissociated from the furnace material in the form of NOx and BOx from the boron nitride materials (BN and pBN) used in the furnace material, and nitrogen (N) and boron (B) in the form of NOx and BOx. Therefore, it is considered that there is a property that it is taken into the crystal. In addition, quartz, which is also used for the furnace material, has a property of incorporating carbon oxide (COx), which also becomes a pollution source. Therefore, first, it is tried to reduce the impurity concentration in the CdTe-based semiconductor crystal by lowering the oxygen (O) concentration and the carbon oxide (COx) concentration contained in the CdTe-based semiconductor crystal manufacturing apparatus. It was
より具体的には、ＣｄＴｅ系化合物半導体の結晶成長は、その原料を坩堝に充填して所定時間加熱した後、冷却することにより実施され、その結果、ＣｄＴｅ系化合物半導体のインゴットが生成される。そこで、Ｏ、ＣＯｘの混入源として最も大きいと思われる坩堝や坩堝を保持するサセプター、石英製アンプルなどの炉材（窒化ホウ素、炭素、炉材に含有する水分など）を不活性雰囲気中で加熱することにより、残留水分量を減らして、残留水分に起因する酸素（Ｏ）を減らすことで炉材中の酸素（Ｏ）濃度を下げ、加えて不活性雰囲気中で加熱することで炭素酸化物（ＣＯｘ）濃度も下がるので、ひいてはＣｄＴｅ系化合物半導体の中の不純物濃度を減らすことを試みた。 More specifically, crystal growth of a CdTe-based compound semiconductor is performed by filling the crucible with the raw material, heating the crucible for a predetermined time, and then cooling the raw material. As a result, an ingot of the CdTe-based compound semiconductor is produced. Therefore, furnace materials (boron nitride, carbon, water contained in furnace materials) such as susceptors holding crucibles and crucibles, quartz ampoules, etc., which are considered to be the largest sources of O and COx mixed, are heated in an inert atmosphere. By reducing the amount of residual water and oxygen (O) resulting from the residual water to reduce the concentration of oxygen (O) in the furnace material, and by heating in an inert atmosphere, carbon oxide Since the (COx) concentration also decreases, it was attempted to reduce the impurity concentration in the CdTe compound semiconductor.
また、坩堝などの炉材の加熱処理時間とＣｄＴｅ系化合物半導体不純物濃度の関係を調べるため、坩堝等の炉材の加熱は、加熱温度を同一とし、加熱時間を１か月、２週間、１週間、１日、及び１２時間と変えて、不活性雰囲気下で行ない、加熱時間の異なる坩堝等の炉材を用意した。加熱処理された種々の炉材を用いて、ＣｄＴｅ系化合物半導体のインゴットを育成し、さらに育成された各インゴットから基板表面の結晶方位が（１１１）面となるように円盤状の基板を切り出した。各ＣｄＴｅ系化合物半導体基板中の不純物元素の濃度は、グロー放電質量分析装置（ＧＤＭＳ：Glow Discharge Mass Spectrometry）を用いて評価した。また、正孔のμτ（ｈ）値は、該円盤状の基板をダイシングにより矩形に加工し、基板の表裏面を鏡面研磨処理を施した後、当該基板の一方の主面にＰｔオーミック電極、もう一方の主（裏）面にＩｎショットキー電極を形成して素子基板を作製し、所定値の電圧を印加しながら、標準放射線源より放射線を素子基板に照射し、生成された正孔キャリアを電気信号として取り出し、多チャンネル波高分析装置（ＭＣＡ）を介して測定した。このようにして、測定された不純物の濃度と正孔のμτ（ｈ）値との相関を調べた。 Further, in order to investigate the relationship between the heat treatment time of the furnace material such as the crucible and the concentration of the CdTe-based compound semiconductor impurity, the heating temperature of the furnace material such as the crucible was the same, and the heating time was 1 month, 2 weeks, 1 A furnace material such as a crucible having a different heating time was prepared by performing the heating in an inert atmosphere instead of weekly, daily, and 12 hours. CdTe compound semiconductor ingots were grown using various heat-treated furnace materials, and a disk-shaped substrate was cut from each of the grown ingots so that the crystal orientation of the substrate surface was the (111) plane. .. The concentration of the impurity element in each CdTe-based compound semiconductor substrate was evaluated using a glow discharge mass spectrometer (GDMS: Glow Discharge Mass Spectrometry). In addition, the μτ(h) value of holes is obtained by processing the disk-shaped substrate into a rectangle by dicing, subjecting the front and back surfaces of the substrate to mirror polishing, and then applying a Pt ohmic electrode to one main surface of the substrate. The In Schottky electrode is formed on the other main (back) surface to prepare an element substrate, and while applying a voltage of a predetermined value, the element substrate is irradiated with radiation from a standard radiation source to generate hole carriers Was taken out as an electric signal and measured through a multi-channel wave height analyzer (MCA). In this way, the correlation between the measured impurity concentration and the μτ(h) value of holes was examined.
不純物濃度と正孔のμτ（ｈ）値との相関によれば、酸素（Ｏ）のみならず、ボロン（Ｂ）、炭素（Ｃ）、及び窒素（Ｎ）もトラップ準位を形成し、正孔のμτ（ｈ）の低下に寄与すると考えられる。特に、ボロン（Ｂ）及び窒素（Ｎ）は、他の不純物に比べて、正孔のμτ（ｈ）値を低下させる効果が大きいことが分かった。 According to the correlation between the impurity concentration and the μτ(h) value of holes, not only oxygen (O) but also boron (B), carbon (C), and nitrogen (N) form trap levels, and It is considered to contribute to the decrease of μτ(h) of the holes. In particular, it has been found that boron (B) and nitrogen (N) have a larger effect of reducing the μτ(h) value of holes than other impurities.
そこで、本発明によれば、正孔のμτ（ｈ）値を下げる主たる原因となるボロン（Ｂ）の濃度が２０ａｔｏｍ ｐｐｂ以下であることを特徴としたＣｄＴｅ系化合物半導体基板（１）であり、さらに、ボロン（Ｂ）の濃度が２０ａｔｏｍ ｐｐｂ以下であり、且つ、窒素（Ｎ）の濃度が１５ａｔｏｍ ｐｐｂ以下であることを特徴としたＣｄＴｅ系化合物半導体基板（２）が提供される。 Therefore, according to the present invention, a CdTe-based compound semiconductor substrate (1) is characterized in that the concentration of boron (B), which is a main cause of lowering the μτ(h) value of holes, is 20 atom ppb or less, Further, there is provided a CdTe compound semiconductor substrate (2) characterized in that the concentration of boron (B) is 20 atom ppb or less and the concentration of nitrogen (N) is 15 atom ppb or less.
本発明によれば、ボロン（Ｂ）濃度と窒素（Ｎ）濃度との和が３０ａｔｏｍ ｐｐｂ以下である、上記（１）及び（２）に記載のＣｄＴｅ系化合物半導体基板（３）が提供される。 According to the present invention, there is provided the CdTe compound semiconductor substrate (3) according to the above (1) and (2), wherein the sum of the boron (B) concentration and the nitrogen (N) concentration is 30 atom ppb or less. ..
本発明によれば、正孔の移動度μと該正孔の寿命τの積であるμτ積（ｈ）が５．０×１０−５ｃｍ２／Ｖ以上であることを特徴とする、上記（１）〜（３）のいずれかに記載のＣｄＴｅ系化合物半導体基板（４）が提供される。
本発明によれば、上記（１）〜（４）のいずれか１項に記載のＣｄＴｅ系化合物半導体基板を用いて作製されたことを特徴とするＣｄＴｅ系半導体直接検出型放射線検出素子が提供される。
According to the present invention, the μτ product (h), which is the product of the hole mobility μ and the hole lifetime τ, is 5.0×10 −5 cm 2 /V or more. A CdTe compound semiconductor substrate (4) according to any one of (1) to (3) is provided.
According to the present invention, there is provided a CdTe-based semiconductor direct detection type radiation detection element manufactured by using the CdTe-based compound semiconductor substrate according to any one of (1) to (4) above. It
本発明によれば、前記ＣｄＴｅ系化合物半導体の対向する面には、ＩｎまたはＰｔからなる電極が設けられていることを特徴する、上記（１）〜（５）のいずれか１項に記載の半導体直接検出型放射線検出素子が提供される。 According to the present invention, there is provided an electrode made of In or Pt on the facing surface of the CdTe-based compound semiconductor, according to any one of the above (1) to (5). A semiconductor direct detection type radiation detection element is provided.
本発明にかかる半導体直接検出型放射線検出素子は、ショットキー素子であり、正孔が移動する側の電極がインジウム（Ｉｎ）であり、電子が移動する側の電極がプラチナ（Ｐｔ）であることが望ましいが、本発明の本質はＣｄＴｅ系半導体材料を対象とし、素子の種類、電極金属の種類によらず適用できるものである。 The semiconductor direct detection type radiation detection element according to the present invention is a Schottky element, in which the electrode on the side where holes move is indium (In) and the electrode on the side where electrons move is platinum (Pt). However, the essence of the present invention is applicable to CdTe-based semiconductor materials regardless of the type of element and the type of electrode metal.
本発明によれば、ＣｄＴｅ系半導体に含まれる不純物のうちボロン（Ｂ）、炭素（Ｃ）、窒素（Ｎ）、及び酸素（Ｏ）の濃度を所定濃度以下に抑えることが可能となった。さらに、ボロン（Ｂ）、炭素（Ｃ）、窒素（Ｎ）、及び酸素（Ｏ）の濃度を所定濃度以下とすることにより、正孔のμτ（ｈ）値を高めるのみならず、正孔のμτ（ｈ）値が大きくばらつくことを抑制でき、再現性よく、高いμτ（ｈ）値を有するＣｄＴｅ系化合物半導体基板を作製することが可能となった。特に、ボロン（Ｂ）濃度を所定の濃度以下に抑えることによって、さらには、ボロン（Ｂ）濃度と窒素（Ｎ）濃度を各々所定の濃度以下に抑えることによって、組成が同じＣｄＴｅ系化合物半導体であっても制御しきれなかった正孔のμτ（ｈ）値のばらつきを再現性よく抑えることが可能となった。 According to the present invention, it has become possible to suppress the concentrations of boron (B), carbon (C), nitrogen (N), and oxygen (O) among the impurities contained in the CdTe-based semiconductor to below a predetermined concentration. Further, by setting the concentrations of boron (B), carbon (C), nitrogen (N), and oxygen (O) to be equal to or lower than a predetermined concentration, not only the μτ(h) value of holes is increased, but also the It is possible to suppress the large variation of the μτ(h) value, and it is possible to manufacture a CdTe compound semiconductor substrate having a high μτ(h) value with good reproducibility. In particular, by keeping the boron (B) concentration below a predetermined concentration, and further by keeping the boron (B) concentration and the nitrogen (N) concentration below a predetermined concentration respectively, a CdTe-based compound semiconductor having the same composition is obtained. It was possible to suppress the variation in the μτ(h) value of holes, which could not be controlled even if there was any, with good reproducibility.
以下、図面を参照して本発明に係るＣｄＴｅ系半導体及びその製造方法について説明する。但し、本発明に係るＣｄＴｅ系半導体及びその製造方法は多くの異なる態様で実施することが可能であり、以下に示す実施の形態の記載内容に限定して解釈されるものではない。なお、本実施の形態で参照する図面において、同一部分または同様な機能を有する部分には同一の符号を付し、その繰り返しの説明は省略する。 Hereinafter, a CdTe-based semiconductor and a method for manufacturing the same according to the present invention will be described with reference to the drawings. However, the CdTe-based semiconductor and the method for manufacturing the same according to the present invention can be implemented in many different modes, and should not be construed as being limited to the description of the embodiments below. Note that in the drawings referred to in this embodiment, the same portions or portions having similar functions are denoted by the same reference numerals, and repeated description thereof is omitted.
図１は、ＣｄＴｅ系半導体を、垂直温度勾配凝固法（ＶＧＦ法）により成長させるための結晶成長装置の概略構成図である。坩堝内で融解した原料融液の一端から徐々に固化を行い、結晶（単結晶及び多結晶を含む。）を育成する方法である。この成長方法は、結晶成長方向の温度勾配が小さいため低転位密度の結晶が容易に得られるという長所を有する。 FIG. 1 is a schematic configuration diagram of a crystal growth apparatus for growing a CdTe-based semiconductor by a vertical temperature gradient solidification method (VGF method). In this method, a crystal (including a single crystal and a polycrystal) is grown by gradually solidifying from one end of the raw material melt melted in the crucible. This growth method has an advantage that a crystal with a low dislocation density can be easily obtained because the temperature gradient in the crystal growth direction is small.
図１中、符号２００は常圧容器を示し、この常圧容器２００の中心にはＣｄを充填するリザーバ部２０１ａを有する石英アンプル２０１が配置されている。また、石英アンプル２０１内にはｐＢＮ（ｐｙｒｏｌｙｔｉｃ Ｂｏｒｏｎ Ｎｉｔｒｉｄｅ）製坩堝２０３が配置され、石英アンプル２０１を包囲するようにヒータ２０２が設けられている。ヒータ２０２は、図１に示すように坩堝２０３に対応する部分とリザーバ部２０１ａに対応する部分とを別々の温度に加熱でき、かつ常圧容器２００内の温度分布を細かく制御できる３段の多段型構造を有する。
In FIG. 1,
まず、結晶成長装置内のリザーバ部２０１ａを有する石英アンプル２０１及び坩堝２０３の炉材を、王水を用いて洗浄した後、さらに超純水で洗浄した。次に、窒素ガス雰囲気下で、ヒータ２０２を用いて１５０℃にて加熱する。加熱時間は、１か月、２週間、１週間、１日、及び１２時間と変えて、加熱温度は同じであるが、加熱時間の異なる坩堝等の炉材を用意した。なお、本実施例では、不活性ガスとして窒素ガスを用いたが、あくまで一例であって、例えばアルゴンガスでも構わない。
First, the
加熱時間が各々異なる炉材を用いて、垂直温度勾配凝固法（ＶＧＦ）によりＣｄ０．９Ｚｎ０．１Ｔｅ結晶を育成した。具体的には、まず、石英アンプル２０１のリザーバ部２０１ａに易揮発性元素であるＣｄ単体２０４を入れるとともに、ｐＢＮ製坩堝２０３にＣｄＺｎＴｅの結晶原料２０５を入れて石英アンプル２０１内に配置した後、石英アンプル２０１を真空封止した。
Cd 0.9 Zn 0.1 Te crystals were grown by the vertical temperature gradient solidification method (VGF) using furnace materials having different heating times. Specifically, first, Cd
次に、ヒータ２０２で加熱昇温して坩堝２０３内のＣｄＴｅ原料２０５を融解した後、ヒータ２０２でリザーバ部２０１ａを７８０℃に加熱して、Ｃｄ蒸気圧を０．１１６ＭＰａに制御を行うとともに、坩堝２０３を１１００℃に加熱した。さらに、常圧容器２００内に所望の温度分布が生じるように各ヒータへの供給電力量を制御装置（図示しない）で制御しながら加熱炉内の温度を０．１℃／ｈｒの降温速度で徐々に下げて、約２００時間かけて原料融液の表面から下方に向かってＣｄＺｎＴｅ結晶を成長させた。
Next, after heating by the
各々異なる時間で加熱処理された炉材を用いて育成されたＣｄＺｎＴｅ結晶中の不純物濃度はグロー放電質量分析装置（ＧＤＭＳ）を用いて評価された。また、各々異なる時間で加熱処理された炉材を用いて育成されたＣｄＴｅ結晶の正孔のμτ（ｈ）値の測定は、以下の方法で実施した。すなわち、育成されたＣｄＴｅ結晶のインゴットから基板表面の結晶方位が（１１１）面となるように円盤状に基板を切り出し、さらに円盤状の基板を矩形に加工して、基板サイズが４×４×１．４ｍｍ３であるＣｄＺｎＴｅ基板を作製した。次に、基板の表裏面を鏡面研磨した後、メタノール、アセトン等の有機溶剤に浸漬し、室温で超音波洗浄することで、基板に付着した異物を除去し、さらに、臭化水素、臭素及び水を混合したエッチング液に基板を浸漬して、室温で基板の研磨面の加工変質層を除去した。このようにして、洗浄処理されたＣｄＺｎＴｅ基板の（１１１）面の一方の面には無電解めっきにてＰｔ膜を５０ｎｍ堆積し、（−１−１−１）面の他方の面には真空蒸着にてＩｎ膜を３００ｎｍ堆積してショットキー素子を作製した（図２）。 The impurity concentration in the CdZnTe crystal grown by using the furnace material heat-treated at different times was evaluated by using a glow discharge mass spectrometer (GDMS). Further, the measurement of the μτ(h) value of the holes of the CdTe crystal grown by using the furnace material heat-treated at different times was performed by the following method. That is, a disc-shaped substrate was cut out from a grown CdTe crystal ingot so that the crystal orientation of the substrate surface was the (111) plane, and the disc-shaped substrate was processed into a rectangle to obtain a substrate size of 4×4×. A CdZnTe substrate having a size of 1.4 mm 3 was produced. Next, after mirror-polishing the front and back surfaces of the substrate, immersed in an organic solvent such as methanol and acetone, ultrasonic cleaning at room temperature to remove foreign matter attached to the substrate, further hydrogen bromide, bromine and The substrate was immersed in an etching liquid mixed with water to remove the work-affected layer on the polished surface of the substrate at room temperature. In this way, a Pt film having a thickness of 50 nm is deposited on one surface of the (111) surface of the CdZnTe substrate cleaned by electroless plating, and the other surface of the (-1-1-1) surface is vacuumed. An In film was deposited to a thickness of 300 nm by vapor deposition to produce a Schottky device (FIG. 2).
これに、アメリシウム−２４１（Ａｍ２４１）を核種とした標準放射線源（（社）日本アイソトープ協会）を１０ｍｍの間隔を置いてＩｎ膜側に配置し、Ａｍ２４１から出る放射線をショットキー素子が検出できるようにした。この状態でショットキー素子に２５０、５００、７００、９００Ｖの電圧を印加すると、ショットキー素子内に入射したＡｍ２４１からの放射線により素子内部で電子、正孔のキャリアが生成される。生成されたキャリアは印加されている電場に沿って、互いに相反する電位の方向に進むが、Ａｍ２４１線源の位置がＩｎ電極側に近いことから素子から取り出されるキャリアは正孔のみで、電子はＰｔ側に移動中に再結合で消失する。 A standard radiation source using Americium-241 (Am241) as a nuclide (Japan Isotope Association) is placed on the In film side at an interval of 10 mm so that the Schottky element can detect the radiation emitted from Am241. I chose When a voltage of 250, 500, 700 or 900 V is applied to the Schottky element in this state, carriers of electrons and holes are generated inside the element by the radiation from the Am 241 incident on the Schottky element. The generated carriers proceed in the directions of potentials opposite to each other along the applied electric field, but since the position of the Am241 radiation source is close to the In electrode side, the only carriers extracted from the element are holes, and the electrons are It disappears by recombination while moving to the Pt side.
Ｉｎ電極を介して取り出された電気信号は多チャンネル波高分析装置（ＭＣＡ）により信号処理される。ピーク位置はμτ（ｈ）×（結晶内電場）に単調増加で依存するため、電圧を変えて結晶内電場の値を変化させた上でピーク位置の変化を調べることでμτ（ｈ）の値を知ることができる。 The electric signal taken out through the In electrode is processed by a multi-channel pulse height analyzer (MCA). Since the peak position depends on μτ(h) × (electric field in the crystal) with a monotonic increase, the value of μτ(h) can be calculated by examining the change in the peak position after changing the value of the electric field in the crystal by changing the voltage. You can know
各々異なる時間で育成前に加熱処理された炉材を用いて育成させたＣｄ０．９Ｚｎ０．１Ｔｅ単結晶について、ＧＤＭＳによる不純物濃度の評価結果、及び作製したショットキー素子から評価した正孔のμτ（ｈ）値を表１に示す。 The Cd 0.9 Zn 0.1 Te single crystal grown using the furnace material that had been heat-treated before the growth at different times were evaluated by the GDMS impurity concentration evaluation results and the positive Schottky device evaluation. The μτ(h) values of the holes are shown in Table 1.
表１によれば、結晶育成前の炉材の加熱時間が長い程、酸素（Ｏ）濃度が低くなっていく傾向がわかる。他の不純物（Ｂ、Ｃ、Ｎ）については、ばらつきが見られるが、特に、加熱時間が１か月になると、どの不純物についても低くなっている。したがって、育成前に炉材を加熱することによって、結晶成長装置内の残留水分量を減らし、ひいてはＣｄＴｅ系半導体内の酸素（Ｏ）濃度を減らすことが可能となることが分かる。また、比較例２のデータに着目すると、窒素（Ｎ）濃度が２．０ａｔｏｍ ｐｐｂ程度と極めて低くなっているが、そのような場合でも正孔のμτ（ｈ）値は２．３×１０−５ｃｍ２／Ｖと低い値となっていた。したがって、単純に、１つの不純物濃度を低減するだけでは、正孔のμτ（ｈ）が増大化する傾向を得ることができないと言える。 Table 1 shows that the longer the heating time of the furnace material before crystal growth, the lower the oxygen (O) concentration. There are variations in the other impurities (B, C, N), but especially when the heating time is one month, all the impurities are low. Therefore, it can be seen that by heating the furnace material before the growth, it is possible to reduce the amount of residual water in the crystal growth apparatus, and thus reduce the oxygen (O) concentration in the CdTe-based semiconductor. Also, focusing on the data of Comparative Example 2, the nitrogen (N) concentration is as low as about 2.0 atom ppb, and even in such a case, the μτ(h) value of holes is 2.3×10 −. The value was as low as 5 cm 2 /V. Therefore, it can be said that the tendency of increasing μτ(h) of holes cannot be obtained by simply reducing the concentration of one impurity.
特に、比較例２では、上述のように、窒素（Ｎ）濃度が２．０ａｔｏｍ ｐｐｂと極めて低い濃度であるが、ボロン（Ｂ）濃度が１２０ａｔｏｍ ｐｐｂと高いことから、正孔のμτ（ｈ）値は２．３×１０−５ｃｍ２／Ｖと低い値になっていると考えられる。 Particularly, in Comparative Example 2, as described above, the nitrogen (N) concentration is as low as 2.0 atom ppb, but the boron (B) concentration is as high as 120 atom ppb. The value is considered to be as low as 2.3×10 −5 cm 2 /V.
以上のように、ボロン（Ｂ）濃度が正孔のμτ（ｈ）に大きく影響を与えていることが分かる。 As described above, it can be seen that the boron (B) concentration has a great influence on μτ(h) of holes.
さらに正孔のμτ（ｈ）の各不純物の濃度への依存性を見るために、各々異なる時間で育成前に加熱処理された炉材を用いて育成させたＣｄ０．９Ｚｎ０．１Ｔｅ結晶に含まれる各不純物の濃度とμτ（ｈ）との依存性をプロットしたグラフを作成した（図３ないし図８）。これらのグラフによって、不純物濃度と正孔のμτ（ｈ）との間には以下の傾向があることが分かった。 Further, in order to check the dependence of μτ(h) of holes on the concentration of each impurity, Cd 0.9 Zn 0.1 Te grown by using a furnace material which was heat-treated before the growth at different times. Graphs were prepared by plotting the dependence of the concentration of each impurity contained in the crystal on μτ(h) (FIGS. 3 to 8). From these graphs, it was found that there is the following tendency between the impurity concentration and the hole μτ(h).
ボロン（Ｂ）の濃度と正孔のμτ（ｈ）との依存性をプロットしたグラフ(図３）によれば、ボロン（Ｂ）濃度は、正孔のμτ（ｈ）とかなり強い相関があることが分かる。ボロン（Ｂ）濃度が高ければ高いほど正孔のμτ（ｈ）は低くなり、ボロン（Ｂ）濃度が低ければ低いほど正孔のμτ（ｈ）は高くなる傾向があるということができる。特にボロン（Ｂ）の場合、その濃度を２０ａｔｏｍ ｐｐｂ以下に抑えると正孔のμτ（ｈ）は急激に高くなる傾向がある。 According to the graph (FIG. 3) plotting the dependency of the concentration of boron (B) and μτ(h) of holes, the boron (B) concentration has a fairly strong correlation with μτ(h) of holes. I understand. It can be said that the higher the boron (B) concentration, the lower the hole μτ(h), and the lower the boron (B) concentration, the higher the hole μτ(h). Particularly in the case of boron (B), if the concentration thereof is suppressed to 20 atom ppb or less, μτ(h) of holes tends to rapidly increase.
また、ＣｄＴｅ系半導体に含まれるボロン（Ｂ）濃度及び窒素（Ｎ）の濃度の和と正孔のμτ（ｈ）値との関係をプロットした図７によれば、ボロン（Ｂ）濃度と窒素（Ｎ）濃度の合計値は、正孔のμτ（ｈ）値との間に、より明確な強い相関が見られた（図７）。図７は、ボロン（Ｂ）濃度と窒素（Ｎ）濃度の合計値が低くなれば正孔のμτ（ｈ）値が高くなり、ボロン（Ｂ）濃度と窒素（Ｎ）濃度の合計値が高くなれば正孔のμτ（ｈ）値が低くなる傾向を示している。一方で、ボロン（Ｂ）濃度、炭素（Ｃ）濃度、窒素（Ｎ）濃度、酸素（Ｏ）濃度の合計値と正孔のμτ（ｈ）との関係は、図８からも明らかなとおり、ボロン（Ｂ）濃度、炭素（Ｃ）濃度、窒素（Ｎ）濃度、酸素（Ｏ）濃度の合計値が小さい場合には、ある程度の相関（不純物濃度の合計値が小さければ、正孔のμτ（ｈ）は高くなる）はあるが、不純物濃度の合計値が大きくなると、単純なμτ（ｈ）の減少傾向が見られず、ばらついている。 Further, according to FIG. 7 in which the relationship between the sum of the concentration of boron (B) and the concentration of nitrogen (N) contained in the CdTe-based semiconductor and the μτ(h) value of holes is plotted, the boron (B) concentration and the nitrogen A clearer strong correlation was found between the total value of (N) concentration and the μτ(h) value of holes (FIG. 7 ). In FIG. 7, the lower the total value of the boron (B) concentration and the nitrogen (N) concentration, the higher the μτ(h) value of the holes, and the higher the total value of the boron (B) concentration and the nitrogen (N) concentration. If so, the μτ(h) value of holes tends to decrease. On the other hand, the relationship between the total value of boron (B) concentration, carbon (C) concentration, nitrogen (N) concentration, and oxygen (O) concentration and μτ(h) of holes is as shown in FIG. When the total value of the boron (B) concentration, the carbon (C) concentration, the nitrogen (N) concentration, and the oxygen (O) concentration is small, some correlation (if the total value of the impurity concentration is small, μτ( Although h) becomes high), when the total value of the impurity concentration becomes large, the simple decreasing tendency of μτ(h) is not seen and varies.
さらに、比較例１及び７に着目すると、以下の傾向が見える。すなわち、比較例１では、ボロン（Ｂ）濃度３５ａｔｏｍ ｐｐｂ、窒素（Ｎ）濃度１０ａｔｏｍ ｐｐｂであり、一方、比較例７のボロン（Ｂ）濃度は２５ａｔｏｍ ｐｐｂ、窒素（Ｎ）濃度４５ａｔｏｍ ｐｐｂとなっており、ボロン（Ｂ）濃度については比較例１の方が高く、窒素（Ｎ）濃度については比較例７の方が高い濃度となっている。正孔のμτ（ｈ）値は、比較例７の方が高いことから、ボロン濃度の低減がμτ（ｈ）を大きくするのに効果があると言える。 Furthermore, focusing attention on Comparative Examples 1 and 7, the following tendencies are seen. That is, in Comparative Example 1, the boron (B) concentration was 35 atom ppb and the nitrogen (N) concentration was 10 atom ppb, while the boron (B) concentration in Comparative Example 7 was 25 atom ppb and the nitrogen (N) concentration was 45 atom ppb. Therefore, the boron (B) concentration is higher in Comparative Example 1 and the nitrogen (N) concentration is higher in Comparative Example 7. Since the value of μτ(h) of holes is higher in Comparative Example 7, it can be said that the reduction of the boron concentration is effective in increasing μτ(h).
以上の考察及び表１より、正孔のμτ（ｈ）は、ボロン（Ｂ）濃度に大きく依存し、窒素（Ｎ）濃度についてはボロン（Ｂ）濃度ほどではないが、正孔のμτ（ｈ）値に影響を及ぼしていることが分かった。具体的には、ボロン（Ｂ）濃度が１８．５ａｔｏｍ ｐｐｂより低く、尚且つ窒素（Ｎ）濃度も３．５ａｔｏｍ ｐｐｂ以下に抑えられている場合は、安定的にかなり高い正孔のμτ（ｈ）値となるＣｄＴｅ系半導体になるということができる。 From the above consideration and Table 1, μτ(h) of holes largely depends on the boron (B) concentration, and the nitrogen (N) concentration is not as high as the boron (B) concentration, but μτ(h) of the holes is high. ) It has been found to affect the value. Specifically, when the boron (B) concentration is lower than 18.5 atom ppb and the nitrogen (N) concentration is suppressed to 3.5 atom ppb or less, μμ(h It can be said that it becomes a CdTe-based semiconductor having a value of ).
また、図７に基づけば、ボロン（Ｂ）濃度と窒素（Ｎ）濃度との和が３０ａｔｏｍ ｐｐｂ以下とすると、正孔のμτ（ｈ）値を高くすることができるといえる。 Further, based on FIG. 7, it can be said that if the sum of the boron (B) concentration and the nitrogen (N) concentration is 30 atom ppb or less, the μτ(h) value of holes can be increased.
以上のとおり、ＣｄＴｅ系半導体の育成時において、ボロン（Ｂ）及び窒素（Ｎ）等の、不純物の混入量を極力減らすことによって、ＣｄＴｅ系化合物半導体の正孔のμτ（ｈ）値を高めるとともに、同じ組成のＣｄＴｅ系化合物半導体において、製造の度毎に、正孔のμτ（ｈ）値がばらつく問題点を再現性よく抑えることが可能となる。 As described above, at the time of growing a CdTe-based semiconductor, the amount of impurities such as boron (B) and nitrogen (N) mixed is reduced as much as possible to increase the μτ(h) value of holes in the CdTe-based compound semiconductor and In the CdTe compound semiconductor having the same composition, it is possible to reproducibly suppress the problem that the μτ(h) value of the holes varies with each production.
なお、今回の一連の実験によって、ＣｄＴｅ系半導体の育成時に、単にＣｄＴｅ系半導体内に混入してくるだけでなく、他の不純物であるボロン（Ｂ）、窒素（Ｎ）及び炭素（Ｃ）を炉材から引き抜き、結晶内に取り込む原因となる酸素（Ｏ）をＣｄＴｅ系半導体の結晶製造装置内から除く方法として、坩堝などの炉材を加熱して残留水分量を減らすことは、有効な手段の１つであることが分かった。坩堝などの炉材の加熱時間に応じて、ＣｄＴｅ系半導体内に取り込まれる不純物の量が減少傾向にあるためである。 In addition, according to the series of experiments this time, when the CdTe-based semiconductor is grown, not only the impurities are simply mixed into the CdTe-based semiconductor, but also other impurities such as boron (B), nitrogen (N) and carbon (C) are added. As a method of removing oxygen (O), which causes extraction from the furnace material and incorporation into the crystal, from the inside of the CdTe-based semiconductor crystal manufacturing apparatus, it is an effective means to reduce the residual water content by heating the furnace material such as a crucible. It turned out to be one of the. This is because the amount of impurities taken into the CdTe-based semiconductor tends to decrease according to the heating time of the furnace material such as the crucible.
本発明の実施例においては、ＣｄＴｅ半導体の例を用いて説明したが、II-VI族化合物半導体である、セレンテルル化カドミウム（CdSeTe）、テルル化亜鉛カドミウム（CdZnTe）、セレンテルル化亜鉛カドミウム（CdZnSeTe）についても不純物であるボロン（Ｂ）、窒素（Ｎ）、炭素（Ｃ）及び酸素（Ｏ）の存在が大きく正孔のμτ（ｈ）値に影響を与えている。したがって、ボロン（Ｂ）及び窒素（Ｎ）の各不純物が入り込む量を極力減らすことによって、正孔のμτ（ｈ）値を高めるとともに、正孔のμτ（ｈ）値のばらつきを抑えることが可能である。 Although the examples of the CdTe semiconductors have been described in the examples of the present invention, the group II-VI compound semiconductors are cadmium selenide tellurium (CdSeTe), zinc cadmium telluride (CdZnTe), zinc cadmium selenide tellurium (CdZnSeTe). As for impurities, the presence of impurities such as boron (B), nitrogen (N), carbon (C) and oxygen (O) greatly affects the μτ(h) value of holes. Therefore, it is possible to increase the μτ(h) value of holes and suppress the variation of μτ(h) values of holes by reducing the amounts of boron (B) and nitrogen (N) entering as much as possible. Is.
上記の実施形態に限られたものではなく、趣旨を逸脱しない範囲で適宜変更することが可能である。 The present invention is not limited to the above-described embodiment, but can be modified as appropriate without departing from the spirit of the invention.
２００ 炉心管
２０１ 石英アンプルの結晶育成部
２０１a 石英アンプルのＣｄ蒸気圧印加用リザーバ部
２０２ ヒーター
２０３ 坩堝
２０４ Ｃｄ
２０５ ＣｄＴｅ、又は、ＣｄＺｎＴｅ原料
200
202 heater
203 Crucible
204 Cd
205 CdTe or CdZnTe raw material
Claims (5)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015085337A JP6725212B2 (en) | 2015-04-17 | 2015-04-17 | CdTe compound semiconductor and radiation detection element using the same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP2015085337A JP6725212B2 (en) | 2015-04-17 | 2015-04-17 | CdTe compound semiconductor and radiation detection element using the same |
Related Child Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2019163357A Division JP2019212928A (en) | 2019-09-06 | 2019-09-06 | Cdte-based compound semiconductor and radiation detector using the same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JP2016207752A JP2016207752A (en) | 2016-12-08 |
| JP6725212B2 true JP6725212B2 (en) | 2020-07-15 |
Family
ID=57490245
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP2015085337A Active JP6725212B2 (en) | 2015-04-17 | 2015-04-17 | CdTe compound semiconductor and radiation detection element using the same |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP6725212B2 (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US11552174B2 (en) | 2018-02-09 | 2023-01-10 | Jx Nippon Mining & Metals Corporation | Compound semiconductor and method for producing the same |
| KR102196225B1 (en) * | 2019-02-28 | 2020-12-30 | 에스케이실트론 주식회사 | Method for measuring impurity concentration of silicon wafer |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6445799A (en) * | 1987-08-11 | 1989-02-20 | Sumitomo Electric Industries | Production of cadmium telluride based crystal |
| JPH06345598A (en) * | 1993-06-04 | 1994-12-20 | Japan Energy Corp | CdTe crystal for radiation detection element and manufacturing method thereof |
| JP5427655B2 (en) * | 2010-03-11 | 2014-02-26 | 株式会社日立製作所 | Radiation measurement equipment, nuclear medicine diagnostic equipment |
| JP5621919B2 (en) * | 2011-04-01 | 2014-11-12 | 株式会社島津製作所 | Radiation detector manufacturing method and radiation detector |
| US9437692B2 (en) * | 2012-10-25 | 2016-09-06 | Brookhaven Science Associates, Llc | Production and distribution of dilute species in semiconducting materials |
-
2015
- 2015-04-17 JP JP2015085337A patent/JP6725212B2/en active Active
Also Published As
| Publication number | Publication date |
|---|---|
| JP2016207752A (en) | 2016-12-08 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| JP5953116B2 (en) | Compound semiconductor crystal for radiation detection element, radiation detection element, and radiation detector | |
| Roth | Advantages and limitations of cadmium selenide room temperature gamma ray detectors | |
| JP6310794B2 (en) | Radiation detection element, radiation detector, and manufacturing method of radiation detection element | |
| JP7250919B2 (en) | Method for manufacturing semiconductor wafer, radiation detection element, radiation detector, and compound semiconductor single crystal substrate | |
| Šedivý et al. | Positron annihilation spectroscopy of vacancy-related defects in CdTe: Cl and CdZnTe: Ge at different stoichiometry deviations | |
| TWI688681B (en) | Compound semiconductor and its manufacturing method | |
| JP6725212B2 (en) | CdTe compound semiconductor and radiation detection element using the same | |
| Maslyanchuk et al. | Performance Comparison of X-and $\gamma $-Ray CdTe Detectors With MoO x, TiO x, and TiN Schottky Contacts | |
| Popovych et al. | The effect of chlorine doping concentration on the quality of CdTe single crystals grown by the modified physical vapor transport method | |
| JP7265004B2 (en) | Method for manufacturing semiconductor wafer, radiation detection element, radiation detector, and compound semiconductor single crystal substrate | |
| Franc et al. | Melt growth and post‐grown annealing of semiinsulating (CdZn) Te by vertical gradient freeze method | |
| JP6713341B2 (en) | Compound semiconductor substrate and manufacturing method thereof | |
| Saucedo et al. | Heavy metal doping of CdTe crystals | |
| Shiraki et al. | Improvement of the productivity in the growth of CdTe single crystal by THM for the new PET system | |
| Kochanowska et al. | Growth and Characterization of (Cd, Mn) Te | |
| JP6097854B2 (en) | Method for producing compound semiconductor crystal for radiation detection element | |
| JP2019212928A (en) | Cdte-based compound semiconductor and radiation detector using the same | |
| Sekine et al. | Growth and characterization of CdTe single crystals prepared by the “Liquinert Processed” vertical Bridgman method for radiation detectors | |
| JP7217715B2 (en) | Compound semiconductor substrate and manufacturing method thereof | |
| Zaiour et al. | Preparation of High Purity CdTe for Nuclear Detector: Electrical and Nuclear Characterization | |
| Pavesi et al. | On the role of boron in CdTe and CdZnTe crystals | |
| Zhou et al. | Studies on the deep‐level defects in CdZnTe crystals grown by travelling heater method | |
| Darken et al. | High-purity germanium detectors | |
| Swain et al. | Large volume single crystal growth of cadmium zinc telluride with minimal secondary phases for room temperature radiation detector application | |
| Riabov | Purification and crystal growth of InI and alloys IN1-x TLxI and IN1-xGAxI for application in X-ray and gamma-ray detectors |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| A621 | Written request for application examination |
Free format text: JAPANESE INTERMEDIATE CODE: A621 Effective date: 20171201 |
|
| RD03 | Notification of appointment of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7423 Effective date: 20171201 |
|
| A977 | Report on retrieval |
Free format text: JAPANESE INTERMEDIATE CODE: A971007 Effective date: 20181015 |
|
| A131 | Notification of reasons for refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A131 Effective date: 20181113 |
|
| A521 | Request for written amendment filed |
Free format text: JAPANESE INTERMEDIATE CODE: A523 Effective date: 20190111 |
|
| RD02 | Notification of acceptance of power of attorney |
Free format text: JAPANESE INTERMEDIATE CODE: A7422 Effective date: 20190111 |
|
| A02 | Decision of refusal |
Free format text: JAPANESE INTERMEDIATE CODE: A02 Effective date: 20190611 |
|
| A61 | First payment of annual fees (during grant procedure) |
Free format text: JAPANESE INTERMEDIATE CODE: A61 Effective date: 20200625 |
|
| R151 | Written notification of patent or utility model registration |
Ref document number: 6725212 Country of ref document: JP Free format text: JAPANESE INTERMEDIATE CODE: R151 |
|
| S531 | Written request for registration of change of domicile |
Free format text: JAPANESE INTERMEDIATE CODE: R313531 |
|
| R350 | Written notification of registration of transfer |
Free format text: JAPANESE INTERMEDIATE CODE: R350 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |