JPH09186362A - Group III nitride semiconductor light emitting device - Google Patents

Abstract

(57) Abstract: To increase the emission intensity in the ultraviolet region. A light emitting device having a p-layer (61, 62), an n-layer (4, 3) and a light-emitting layer (5) sandwiched between the p-layer and the n-layer, each layer being made of a group III nitride semiconductor. Thickness is 1 ~ 200nm
And Further, the light emitting layer 5 is Ga _0.92 In _0.08 N, and Si and Zn
Was added at 1 × 10 ¹⁷ to 5 × 10 ¹⁸ / cm ³ . The emission intensity at 380 nm increased five times as compared with the case where the thickness of the light emitting layer 5 was 400 nm.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device using a group III nitride semiconductor with improved band edge emission efficiency.

[0002]

BACKGROUND ART Conventionally, as a light emitting device according to the band edge emission using group III nitride semiconductor, an In _0.08 Ga _0.92 N or Si is used an added In _0.08 Ga _0.92 N elements are known in the light-emitting layer . In this device, light with a wavelength of 380 nm is emitted by recombination of electrons and holes between the Si donor level and the valence band or between the valence band and the conduction band.

[0003]

However, in the light emitting device having this structure, the concentration of carriers injected into the light emitting layer is low, electron-hole recombination hardly occurs, and the light emitting efficiency is not good.

The present invention has been made to solve the above problems, and an object thereof is to improve the emission efficiency of band edge emission in a Group III nitride compound semiconductor light emitting device.

[0005]

According to the invention of claim 1, p
In a light emitting device having a layer, an n layer, and a light emitting layer sandwiched between ap layer and an n layer, each layer being made of a group III nitride semiconductor, a light emitting layer is formed by adding a donor impurity and an acceptor impurity together. Thickness is 1 to 200 nm, and the output light is the emission wavelength due to the transition of electrons between the donor impurity level and the valence band, the conduction band and the acceptor impurity level, or the conduction band and the valence band. It is characterized by The thickness of the light emitting layer 1
By setting it to ~ 200 nm, the effect of confining the injected carriers is improved. As a result, electron transitions between the donor impurity level and the valence band, between the conduction band and the acceptor impurity level, and between the conduction band and the valence band increase depending on the presence of the impurity level. Alternatively, the emission intensity and emission efficiency between the bands increase. The thickness of the light emitting layer is 1 nm
If it is thinner than this, the crystallinity is not good and it is not desirable. However, if it is thinner than 15 nm, it becomes difficult to obtain good uniformity of the interface, so that the thickness of 15 nm or more is more desirable. Further, if the thickness of the light emitting layer is thicker than 200 nm, the effect of confining the injected carriers is lowered, which is not desirable.

The light emitting layer is composed of a quaternary system, a ternary system, a binary system,
In other words, the general formula _{Al x Ga y In 1-XY} N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x
It is possible to use a group III nitride semiconductor represented by + y ≤1). The composition ratio may be appropriately selected from the viewpoint of the relationship between the emission wavelength and the band gap and the lattice matching. Further, a quantum well structure having at least one period or more may be used. Especially,
To obtain emission near 380 nm, the emission layer should be Ga _x In _1-X N (0 ≤
It is desirable that x ≤ 1).

When the thickness of the light emitting layer is set to 1 to 200 nm and the donor impurity and the acceptor impurity are added together, the transition between the donor impurity level and the valence band is increased as compared with the case where only the donor impurity is added. Has been confirmed to be larger.

Donor impurities include silicon (Si) and tellurium.
(Te), sulfur (S), or selenium (Se) can be used, and magnesium (Mg) or zinc (Zn) can be used as an acceptor impurity. These may be selected according to the relationship between the emission wavelength and the band gap.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment In FIG. 1, a light emitting diode 10 has a sapphire substrate 1 on which 500.degree.
An N 2 buffer layer 2 is formed. The buffer layer 2
Over, in turn, a film thickness of about 5.0 [mu] m, the concentration 5 × 10 ¹⁸ / cm high carrier concentration comprising a silicon-doped GaN of ³ n ⁺ layer 3,
A film thickness of about 0.5 μm and a concentration of 5 × 10 ¹⁷ / cm ³ of silicon-doped
N layer 4 made of GaN, In _0.08 Ga with a thickness of about 50 nm and doped with silicon and zinc at 5 × 10 ¹⁸ / cm ³ respectively
Light-emitting layer 5 consisting of _0.92 N, film thickness about 0.5 μm, hole concentration 5
P layer 61 made of Al _0.08 Ga _0.92 N doped with magnesium at a concentration of 10 ¹⁷ / cm ³ and a concentration of 5 10 ²⁰ / cm ³ , film thickness of about 1 μm
m, hole concentration 7 × 10 ¹⁸ / cm ³ , magnesium concentration 5 × 10
^A contact layer 62 made of ²¹ / cm ³ of magnesium-doped GaN is formed. Then, the electrode 7 made of Ni and bonded to the contact layer 62 is formed on the contact layer 62. Further, a part of the surface of the high carrier concentration n ⁺ layer 3 is exposed, and an electrode 8 made of Ni and bonded to the layer 3 is formed on the exposed portion.

Next, a method of manufacturing the light emitting diode 10 having this structure will be described. The light emitting diode 10 includes:
It was manufactured by vapor phase growth by an organometallic compound vapor phase growth method (hereinafter referred to as “M0VPE”). The gas used was NH
₃ and carrier gas H ₂ or N ₂ and trimethylgallium (Ga
(CH _{3) 3)} and (hereinafter referred to as "TMG") and trimethylaluminum (Al (CH _{3) 3)} (hereinafter referred to as "TMA") and trimethyl indium (an In (CH _{3) 3)} (hereinafter "TMI" Note) and silane (S
iH ₄₎ and cyclopentadienyl magnesium _{(Mg (C 5 H 5)} 2)
(Hereinafter referred to as “CP ₂ Mg”) and diethyl zinc (Zn (C ₂ H ₅ ) ₂ ).
(Hereinafter referred to as "DEZ").

First, a 100-400 μm thick single crystal sapphire substrate 1 having an a-plane as a main surface cleaned by organic cleaning and heat treatment is mounted on a susceptor placed in a reaction chamber of a M0VPE apparatus. Next, the sapphire substrate 1 was subjected to gas phase etching at a temperature of 1100 ° C. while flowing H ₂ at a flow rate of 2 liter / min at normal pressure into the reaction chamber.

Next, the temperature is lowered to 400 ° C. and H ₂ is added.
20 liter / min, NH ₃ 10 liter / min, TMA 1.8 × 10 ^-5
Supplying at mol / min, an AlN buffer layer 2 was formed to a thickness of about 500 °. Next, the temperature of the sapphire substrate 1 was set to 1150
° C, H ₂ at 20 liter / min, NH ₃ at 10 liter / min,
TMG is supplied at 1.7 × 10 ^-4 L / min, and silane diluted to 0.86 ppm with H ₂ gas is supplied at 200 ml / min for 70 minutes to obtain a film thickness of about 5 μm.
m, to form a high carrier concentration n ⁺ layer 3 made of GaN doped with silicon at a concentration 5 × 10 ¹⁸ / cm ^3.

Next, the temperature of the sapphire substrate 1 is maintained at 1100 ° C., N ₂ or H ₂ is 10 liter / min, and NH ₃ is 10 liter / min.
Min, TMG 1.12 × 10 ⁻⁴ mol / min, and H ₂ gas to 0.
Silane diluted to 86 ppm was supplied at 10 × 10 ^-9 mol / min for 30 minutes to form an n-layer 4 made of silicon-doped GaN with a film thickness of about 0.5 μm and a concentration of 5 × 10 ¹⁷ / cm ³ . .

Subsequently, the temperature was maintained at 850 ° C. and N ₂ or H _{2 was} added.
20 liter / min, NH ₃ 10 liter / min, TMG 1.53 × 10
^-4 mol / min, TMI 0.02 × 10 ^-4 mol / min, silane diluted to 0.86 ppm with H ₂ gas at 10 × 10 ^-8 mol / min, and DEZ 2 × 10 ^-4 mol / min. In minutes, supply for 15 minutes, thickness 50
An active layer 5 of In _0.08 Ga _0.92 N doped with 5 × 10 ¹⁸ / cm ³ of silicon and zinc, respectively, was formed.

Subsequently, the temperature was maintained at 1100 ° C. and N ₂ or H _{2 was} added.
20 liter / min, NH ₃ 10 liter / min, TMG 1.12 × 10
^-4 mol / min, 0.47 × 10 ^-4 mol / min of TMA and CP ₂ Mg
Was introduced at 2 × 10 ⁻⁴ mol / min for 30 minutes to form a p-layer 61 made of magnesium (Mg) -doped Al _0.08 Ga _0.92 N with a film thickness of about 0.5 μm. The concentration of magnesium in the p-layer 61 is 5 ×
It is 10 ²⁰ / cm ³ . In this state, the p layer 61 is still an insulator having a resistivity of 10 ⁸ Ωcm or more.

Subsequently, the temperature is maintained at 1100 ° C. and N ₂ or H ₂
20 liter / min, NH ₃ 10 liter / min, TMG 1.12 × 10
^-4 mol / min and CP ₂ Mg at a rate of 4 × 10 ^-3 mol / min
After being introduced for 4 minutes, a contact layer 62 made of GaN doped with magnesium (Mg) and having a film thickness of about 1 μm was formed. The magnesium concentration of the contact layer 62 is 5 × 10 ²¹ / cm ³ .
In this state, the contact layer 62 still has a resistivity of 10 ⁸
It is an insulator of Ωcm or more.

The wafer thus obtained was irradiated with an electron beam by using a reflection electron beam diffractometer. Electron beam irradiation conditions were: acceleration voltage 10 kv, sample current 1 μA, beam moving speed 0.2 mm / sec, beam diameter 60 μmφ, vacuum degree 2.1 × 10 ^-5 To
rr. By this electron beam irradiation, the contact layer 62,
The p-layer 61 has hole concentrations of 7 × 10 ¹⁷ / cm ³ and 5 ×, respectively.
It became a p-conduction type semiconductor with a resistivity of 2 Ωcm and 0.8 Ωcm at 10 ¹⁷ / cm ³ . Thus, a wafer having a multilayer structure was obtained.

Next, as shown in FIG. 2, the contact layer 6
A SiO ₂ layer 9 having a thickness of 2000 Å was formed on the No. ₂ layer by sputtering, and a photoresist 10 was applied on the SiO ₂ layer 9. Then, by photolithography, as shown in FIG. 2, on the contact layer 62, the photoresist 1 of the electrode formation site A ^′ for the high carrier concentration n ⁺ layer 3 is formed.
0 was removed. Next, as shown in FIG. 3, the SiO ₂ layer 9 not covered with the photoresist 10 was removed with a hydrofluoric acid-based etching solution.

Next, the contact layer 62 and the p layer 6 which are not covered with the photoresist 10 and the SiO ₂ layer 9 are formed.
1, light emitting layer 5, n layer 4, vacuum degree 0.04 Torr, high frequency power
0.44 W / cm ² and BCl ₃ gas were supplied at a rate of 10 ml / min for dry etching, and then Ar was used for dry etching. In this step, as shown in FIG. 4, a hole A for extracting an electrode from the high carrier concentration n ⁺ layer 3 was formed.

Next, Ni is vapor-deposited uniformly on the entire surface of the sample, photoresist coating, photolithography process,
Through the etching process, as shown in FIG. 1, the electrodes 8 and 7 for the high carrier concentration n ⁺ layer 3 and the contact layer 62 are formed.
Was formed. Then, the wafer treated as described above was cut into each chip to obtain a light emitting diode chip.

The light emitting device thus obtained had a driving current of 20 mA, an emission peak wavelength of 380 nm and an emission intensity of 2 mW. The luminous efficiency was 3%, which was 10 times higher than that of the conventional structure.

The emission spectrum of the light emitting diode 10 manufactured as described above was measured. It is shown by the curve X1 in FIG. It can be seen that the peak wavelength of 380 nm is obtained. On the other hand, light emission is also observed near 440 nm, which corresponds to light emission between the Si donor level and the Zn acceptor level, but it is understood that the emission intensity at 380 nm is about 5 times greater than the emission intensity at 440 nm.

For comparison, the concentrations of Si and Zn in the light emitting layer 5 are the same as those in the above embodiment, and the thickness of the light emitting layer 5 is 400 n.
The emission spectrum of the light emitting diode set to m was measured.
The result is shown by the curve X2 in FIG. In this case, on the contrary, the emission at 440 nm is dominant and its intensity is 380 nm.
It is about 5 times larger than the emission intensity of. This means that when the thickness of the light emitting layer 5 is 400 nm, there is no effect of increasing the emission intensity of 380 nm.

Further, only Si was added to the light emitting layer 5 at the same concentration as in the above-mentioned example to manufacture a light emitting diode having a thickness of the light emitting layer 5 of 300 nm, and the emission spectrum of the light emitting diode was measured. The result is shown by the curve X3 in FIG. In this case, Zn is not added, so 440 nm
Emission is not observed, but the emission intensity at 380 nm is in the emission layer 5.
It is obtained to the same extent as the curve X2 when Si and Zn are added together. This means that when the thickness of the light emitting layer 5 is 300 nm,
This means that the transition between Si donor level and valence band is still small. When the thickness of the light emitting layer 5 is 200 nm or less, 38
It has been confirmed that the emission intensity at 0 nm is about 5 times greater.

The thickness of the light emitting layer 5 capable of increasing the effect of confining the injected carriers is 200 nm or less, and if the thickness is less than 1 nm, the crystallinity deteriorates, and conversely the light emitting efficiency decreases. Therefore, the thickness of the light emitting layer 5 is 1
A range of ~ 200 nm is desirable. Further, in order to improve the uniformity of the interface, the range of 15 to 200 nm is more desirable. further,
The concentration of Si and Zn added to the light emitting layer 5 is 1 × 10 ¹⁷ to 5 × 10 5.
^{At 18} / cm ³ , the emission intensity in the ultraviolet region below 380 nm can be increased.

As described above, according to the present invention, the thickness of the light emitting layer 5 is changed.
1 to 200 nm increases the transition of electrons between the donor impurity level and the valence band, the conduction band and the acceptor impurity level, or between the conduction band and the valence band to improve the emission efficiency. It is possible to control the emission wavelength.

In _0.08 Ga _0.92 N was used for the light emitting layer 5,
A quaternary group III nitride semiconductor such as _0.03 Ga _0.89 In _0.08 N may be used. Further, as the impurities to be added, it is possible to use elements other than Si and Zn. In short, it may be determined in consideration of the required emission wavelength in consideration of the forbidden band width and the type of impurities to be added. That is, in the above embodiment, the emission wavelength is in the ultraviolet region, but the forbidden band width may be determined so that the emission wavelength is in the visible region such as blue or green. Further, the light emitting layer is Al _x Ga _y
A quantum well structure in which at least one layer of In _1-XY N (0 ≦ x ≦ 1, 0 ≦ y ≦ 1, 0 ≦ x + y ≦ 1) is stacked may be used. Further, the light emitting layer 5 is preferably lattice-matched with the other layers 3, 4, 61 and the like. Although the light emitting diode is shown in the above embodiment, the present invention can be applied to a laser diode.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a light emitting diode according to a specific embodiment of the present invention.

FIG. 2 is a sectional view showing a manufacturing process of the light-emitting diode of the embodiment.

FIG. 3 is a sectional view showing a manufacturing step of the light-emitting diode of the embodiment.

FIG. 4 is a sectional view showing a manufacturing step of the light-emitting diode of the same embodiment.

FIG. 5 is a measurement diagram showing emission spectra of various light emitting diodes in which the thickness of the light emitting layer is changed.

[Explanation of symbols]

10 ... Light emitting diode 1 ... Sapphire substrate 2 ... Buffer layer 3 ... High carrier concentration n ⁺ layer 4 ... N layer 5 ... Light emitting layer 61 ... P layer 62 ... Contact layer 7, 8 ... Electrode

Claims (6)

[Claims] 1. A light-emitting device having a p-layer, an n-layer, and a light-emitting layer sandwiched between the p-layer and the n-layer, each layer being made of a group III nitride semiconductor, wherein the light-emitting layer has a donor impurity and an acceptor. Impurities are added together, and the thickness of the light emitting layer is set to 1 to 200 nm, and the output light is output between the donor impurity level and the valence band, the conduction band and the acceptor impurity level, or the conduction band and the valence band. A group III nitride semiconductor light emitting device, characterized in that the emission wavelength is determined by the transition of electrons between and. 2. The light emitting layer comprises Al _x Ga _y In _1-XY N (0 ≦ x ≦ 1, 0
3. The quantum well structure according to claim 1, which has a quantum well structure in which at least one or more layers of ≤y ≤1, 0 ≤x + y ≤1) are stacked.
Group nitride semiconductor light emitting device. 3. The Group III nitride semiconductor light emitting device according to claim 1, wherein the light emitting layer is Ga _x In _{1 -X} N (0 ≦ x ≦ 1). 4. The group III nitride semiconductor light emitting device according to claim 1, wherein the thickness of the light emitting layer is 15 to 200 nm. 5. The donor impurities are silicon (Si) and tellurium.
(Te), sulfur (S), or selenium (Se), and the acceptor impurity is magnesium (Mg) or zinc (Zn). Semiconductor light emitting device. 6. The concentration of impurities added to the light emitting layer is 1 ×
The group III nitride semiconductor light emitting device according to claim 1, wherein the light emitting device has a concentration of 10 ¹⁷ to 5 × 10 ¹⁸ / cm ³ .