CN114597271A - A novel photoelectric position-sensitive detector based on heterojunction two-dimensional electron gas and its preparation method - Google Patents

Abstract

The invention discloses a novel photoelectric position sensitive detector based on heterojunction two-dimensional electron gas and a preparation method thereof, wherein the detector comprises the following components in sequence from top to bottom: metal electrode, CdTe layer, PbTe layer and BaF arranged on four sides₂The substrate, the CdTe layer and the PbTe layer form a heterojunction, two-dimensional electron gas is naturally formed between the interface of the CdTe layer and the PbTe layer, and the two-dimensional electron gas is in ohmic contact with the metal electrode. By adopting the MBE method, the CdTe/PbTe heterojunction is grown, high-concentration and high-mobility two-dimensional electron gas is naturally generated at the interface of the CdTe/PbTe heterojunction, and the working wavelength of the device exceeds visible light and is wide in working waveband, so that the device can cover medium and short infrared wavebands and has excellent linear responsivity thanks to the physical characteristics of the heterojunction material and the novel lateral photovoltaic effect of the two-dimensional electron gas. The device isThe device has the advantages of simple structure, simple and controllable preparation method, low cost, novel and unique working principle, and scientific research and practical value, and the working range covers medium-short infrared wave bands.

Description

A novel photoelectric position-sensitive detector based on heterojunction two-dimensional electron gas and its preparation method

technical field

The patent of the invention belongs to the field of optoelectronic devices, and specifically relates to a novel photoelectric position-sensitive detector based on a two-dimensional electron gas of a heterojunction and a preparation method thereof.

Background technique

Photoelectric position-sensitive (position-sensitive) detectors are one of the most important types of optical sensors. This type of device works based on the lateral photovoltaic effect and can transmit the spatial position information of the incident light spot in the photosensitive area in the form of electrical signals. When a semiconductor heterojunction or metal/semiconductor Schottky junction is illuminated by a light spot, under the diffusion of photogenerated carriers, a lateral potential difference will be generated on the surface of the material, which is called lateral photovoltaic, and its size is closely related to the position of the light spot. Compared with focal plane array detectors, photoelectric potential-sensitive detectors are not only low cost and convenient to use, but also can continuously track the position change of the light spot and have a more accurate positioning function. Engineering and other fields have important application value. Most of the traditional photopotential-sensitive detectors are based on silicon (Si) or silicon dioxide/silicon (SiO ₂ /Si). distributed in different materials. Most of the common commercial products of photopotential sensitive detectors work in the ultraviolet or visible light band, while the devices that work in the infrared band are still in the experimental research stage.

In recent years, a novel lateral photovoltaic effect based on lead telluride/cadmium telluride (CdTe/PbTe) heterojunction two-dimensional electron gas has been reported, and researchers have developed room temperature infrared detection with high sensitivity and high response speed. detector (Zhu J.Q.etal. Lateral photovoltaic mid-infrared detector with a two-dimensional electrongas at the heterojunction interface. Optica, 2020, 7:1394-1401.). Due to lattice distortion and charge transfer, the CdTe/PbTe heterojunction can generate two-dimensional electron gas with high concentration and high mobility at the interface without intentional doping. Benefiting from the unique energy band structure at the interface of the heterojunction, the photogenerated electrons generated in PbTe can cross the tiny conduction band step and enter the two-dimensional electron gas channel, while the photogenerated holes are trapped by the larger valence band step. block outside the channel. In this case, if the heterojunction receives light unevenly, the electron concentration distribution in the two-dimensional electron gas channel will also be uneven, resulting in a potential difference between the two ends of the channel. Lateral photovoltaic effect, so the heterojunction two-dimensional electron gas can be used to develop photoelectric potential sensitive detectors. Since the intrinsic response range of PbTe is in the mid- and short-infrared band, the photopotential detector based on the two-dimensional electron gas of the CdTe/PbTe heterojunction will also work in the mid- and short-infrared band.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a novel photoelectric position-sensitive detector based on a heterojunction two-dimensional electron gas and a preparation method thereof, specifically, a two-dimensional electron based on a lead telluride/cadmium telluride heterojunction interface Gas photoelectric position sensitive detector and preparation method thereof.

The purpose of this invention is to realize through the following scheme:

The invention discloses a novel photoelectric position-sensitive detector based on a heterojunction two-dimensional electron gas. The detectors from top to bottom are: metal electrodes arranged on four sides, a CdTe layer, a PbTe layer and a BaF ₂ substrate, a CdTe The layer and the PbTe layer constitute a heterojunction, and the interface between the CdTe layer and the PbTe layer is a naturally formed two-dimensional electron gas, and the two-dimensional electron gas is in ohmic contact with the metal electrode.

As a further improvement, the metal electrode of the present invention is a Cu electrode.

As a further improvement, the ohmic contact between the two-dimensional electron gas and the metal electrode described in the present invention is achieved by annealing in a vacuum environment, so that the metal electrode diffuses through the CdTe layer.

As a further improvement, the position-sensitive detector of the present invention works based on the lateral photovoltaic effect of the two-dimensional electron gas (5).

As a further improvement, the photoelectric response of the device according to the present invention is derived from the thick thin film PbTe layer (3) in the heterojunction.

The invention also discloses a preparation method of a novel photoelectric potential-sensitive detector based on a heterojunction two-dimensional electron gas. The preparation steps are as follows:

1) Using the molecular beam epitaxy method, grow a CdTe layer and a PbTe layer on the BaF ₂ substrate respectively to form a heterojunction, and the two-dimensional electron gas is naturally formed at the interface of the heterojunction;

2) Photolithography metal electrode pattern on the sample;

3) Deposit a Cu film with a thickness of 50-200 nm on the photoetched sample by magnetron sputtering or electron beam evaporation, and then peel it off to shape the metal electrode;

4) Place the sample in a vacuum environment and anneal it at 100-200°C for 30-60 minutes and then stop.

As a further improvement, in step 1) of the present invention, the thickness of the PbTe layer is 1-3 μm, and the thickness of the CdTe layer is 50-300 nm.

As a further improvement, in the step 1) of the present invention, the surface concentration of the two-dimensional electron gas at room temperature is about 1×10 ¹³ cm ^-2 , and the mobility is about 900 cm ² /V·s. Due to the high concentration and high mobility of the electron gas, the linear responsivity of the position-sensitive detector is excellent.

As a further improvement, the size of the effective working area of the detector according to the present invention is 3mm×3mm.

As a further improvement, in step 4) of the present invention, the ambient air pressure for annealing is lower than 5×10 ^-4 Pa, and the annealing temperature and annealing time are respectively 100-200° C. and 30-60 min, so that the Cu electrode can pass through completely. The CdTe layer forms a good ohmic contact with the two-dimensional electron gas.

The beneficial effects of the present invention are:

The invention provides a novel photoelectric potential-sensitive detector based on a heterojunction two-dimensional electron gas and a preparation method thereof. A CdTe/PbTe heterojunction was grown by the MBE method, and a two-dimensional electron gas with high concentration and high mobility was naturally generated at the interface, which benefited from the physical properties of the heterojunction material and the novel lateral direction of the two-dimensional electron gas. Photovoltaic effect, the working wavelength of the device exceeds visible light, and the working band is also very wide, covering the mid- and short-infrared bands, and its linear responsivity is excellent. The device has simple structure, simple and controllable preparation method, low cost, novel and unique working principle, and its working range covers the mid- and short-infrared bands. application prospects.

The metal electrode of the present invention is a Cu electrode, and the work function of the electrode is matched with the CdTe layer, thereby preventing the CdTe layer from hindering the collection of photogenerated carriers by the metal electrode.

The ohmic contact between the 2D electron gas and the metal electrode is achieved by annealing in a vacuum environment to diffuse the metal electrode through the CdTe layer.

Potential-sensitive detectors work based on the lateral photovoltaic effect of two-dimensional electron gas. Due to lattice distortion and charge transfer, CdTe/PbTe heterojunctions can generate high concentration and high mobility at the interface without intentional doping. rate of two-dimensional electron gas. Benefiting from the unique energy band structure at the interface of the heterojunction, the photogenerated electrons generated in PbTe can cross the tiny conduction band step and enter the two-dimensional electron gas channel, while the photogenerated holes are trapped by the larger valence band step. Blocked outside the channel, in this case, if the heterojunction receives uneven light, the electron concentration distribution in the two-dimensional electron gas channel will also be uneven, resulting in a potential difference across the channel, which is the CdTe/PbTe heterogeneity The lateral photovoltaic effect of the junction two-dimensional electron gas, and the position-sensitive detector is based on this effect.

The photoelectric response of the device comes from the thick thin film PbTe layer in the heterojunction. Since the intrinsic response range of PbTe is located in the mid and short infrared band, the position-sensitive detector also works in the mid and short infrared band, and the working band is wider. .

Description of drawings

1 is a plan view and a cross-sectional view of the prepared photoelectric potential-sensitive detector;

1 is the metal electrode, 2 is the CdTe layer, 3 is the PbTe layer, 4 is the BaF ₂ substrate, and 5 is the two-dimensional electron gas;

Figure 2 is the current-voltage (I-V) curve of the two electrodes on opposite sides of the device in the x-direction;

Figure 3 is the photocurrent response spectrum of the device. During the test, a bias voltage of 0.1V is applied to the two electrodes on the opposite side in the x direction of the device;

Figure 4 is the lateral photovoltaic response curve of the device along the x-direction under 1064nm laser irradiation;

Figure 5 is the lateral photovoltaic response curve of the device under 1064 nm laser irradiation along the y-direction.

Detailed ways

The present invention discloses a novel photoelectric position-sensitive detector based on a heterojunction two-dimensional electron gas 5. FIG. 1 is a plan view and a cross-sectional view of the prepared photoelectric position-sensitive detector; the sensitive detectors are arranged as follows from top to bottom: On the four sides of the metal electrode 1, the CdTe layer 2, the PbTe layer 3 and the BaF2 substrate 4, the CdTe layer 2 and the PbTe layer 3 form a heterojunction, and the interface between the CdTe layer 2 and the PbTe layer 3 is a naturally formed two-dimensional electron The gas 5 and the two-dimensional electron gas 5 are in ohmic contact with the metal electrode 1 .

The metal electrode 1 is a Cu electrode, and the ohmic contact between the two-dimensional electron gas 5 and the metal electrode 1 is achieved by annealing in a vacuum environment to make the metal electrode 1 diffuse through the CdTe layer 2. The detector is based on two-dimensional The lateral photovoltaic effect of the electron gas 5 works, and the photoelectric response of the device originates from the thick thin film PbTe layer 3 in the heterojunction.

The invention also discloses a preparation method of a novel photoelectric position-sensitive detector based on the heterojunction two-dimensional electron gas 5. By designing and growing the CdTe/PbTe heterojunction, the two-dimensional electron gas 5 is naturally generated at the interface, Thus, it has a new type of lateral photovoltaic effect; electrodes are deposited on the surface of the heterojunction to define a photosensitive region, and at the same time, ohmic contact between the electrodes and the two-dimensional electron gas 5 at the interface is achieved. The present invention includes the following steps:

1) Growth of CdTe/PbTe heterojunction:

A thicker PbTe film was grown on the newly cleaved barium fluoride (BaF ₂ ) substrate by molecular beam epitaxy (MBE), followed by a thinner CdTe film, so that the CdTe/PbTe heterogeneity The knot has grown.

2) Preparation of photoelectric potential sensitive detector:

Photolithography electrode area, cover the area other than the electrode area with photoresist; use magnetron sputtering or electron beam evaporation to deposit a copper (Cu) metal film with a thickness of 100 nm, and then peel off the pattern as the device electrode; The sample is annealed in a vacuum environment to form ohmic contact between the electrode and the two-dimensional electron gas 5 channel, and the device is then fabricated.

The thickness of the PbTe layer 3 is 1-3 μm, the thickness of the CdTe layer 2 is 50-300 nm, the surface concentration of the two-dimensional electron gas 5 at room temperature is about 1×10 ¹³ cm ^-2 , and the mobility is about 900 cm ² /V· s, the size of the effective working area of the detector is 3mm×3mm, the ambient air pressure for annealing is lower than 5×10 ^-4 Pa, and the annealing temperature and annealing time are 100-200°C and 30-60min, respectively.

The technical scheme of the present invention is further described below by specific embodiments:

Preparation process and structure

A. Growth heterojunction

A layer of PbTe layer 3 with a thickness of 1 μm and a layer of CdTe layer 2 with a thickness of 100 nm are successively grown on the newly cleaved BaF2 substrate 4 by the MBE method to form a CdTe/PbTe heterojunction. at the user's interface.

B. Photolithography Metal Electrode 1 Pattern

A uniform layer of AZ5350 photoresist was applied on the surface of the heterojunction, and then it was baked. Under the lithographic mask printed with the electrode pattern, the sample is subjected to ultraviolet exposure and development successively, so that the electrode pattern on the lithographic plate is copied to the surface of the heterojunction.

C. Preparation of metal electrodes 11

A Cu film with a thickness of 100 nm is deposited on the photoetched sample by methods such as magnetron sputtering or electron beam evaporation, and then the sample is soaked in acetone for stripping, and the metal electrode 11 is formed. Next, the sample was placed in a vacuum environment and annealed at 100°C for 30 minutes and then stopped, at which time Cu had diffused through the CdTe layer 2 and was in direct contact with the two-dimensional electron gas 5 channel.

From top to bottom, the sensitive detectors are: metal electrodes 1, CdTe layer 2, PbTe layer 3 and BaF2 substrate 4 arranged on four sides, CdTe layer 2 and PbTe layer 3 form a heterojunction, CdTe layer 2 and PbTe layer 3 Between the interfaces is a naturally formed two-dimensional electron gas 5, and the two-dimensional electron gas 5 is in ohmic contact with the metal electrode 1.

Tests and Results

Figure 2 is the current-voltage (I-V) curve of the two electrodes on the opposite side in the x-direction of the device. The results in the figure show that there is an obvious linear relationship between the current and the voltage, which indicates that the relationship between the electrode 1 and the two-dimensional electron gas 5 is Perfect ohmic contact. Figure 3 is the photocurrent response spectrum of the device. During the test, a bias voltage of 0.1V was applied to the two electrodes on the opposite sides in the x direction of the device. The cut-off wavelength is about 4μm, which corresponds to the band gap of PbTe, which proves that the photoelectric response of the device comes from the intrinsic properties of PbTe. response. It is worth mentioning that the short-wave cut-off of the photocurrent spectrum at 1 μm in Figure 3 is not because the device loses its response, but because the light extraction efficiency of the test system here is very low, and the device hardly receives infrared radiation. The photocurrent spectrum of the device shows that the new photopotential-sensitive detector has a wide operating wavelength range, which can cover the mid- and short-infrared bands. Figure 4 is the lateral photovoltaic response curve of the device along the x direction under 1064nm laser irradiation, and Figure 5 is the lateral photovoltaic response curve of the device along the y direction under 1064nm laser irradiation. The results shown in the figure show that the linear responsivity of the device Well, the nonlinearities in the two directions are 1.9% and 2.2%, respectively, and their response sensitivities are basically the same, which ensures the accuracy of the device when applied to two-dimensional positioning. In conclusion, the novel photoelectric potential-sensitive detector of the present invention has a wide working band and excellent response performance, can be used for two-dimensional precise positioning, and has great application value in many fields.

The above are only the preferred embodiments of the present invention. It should be pointed out that for those skilled in the art, without departing from the core technical features of the present invention, several improvements and modifications can be made. These improvements and retouching should also be regarded as the protection scope of the present invention.

Claims (10)

1. a novel photoelectric position-sensitive detector based on heterojunction two-dimensional electron gas, it is characterized in that, described detector is sequentially from top to bottom: metal electrodes (1), CdTe layers (2) arranged on four sides. ), a PbTe layer (3) and a BaF ₂ substrate (4), the CdTe layer (2) and the PbTe layer (3) form a heterojunction, and the interface between the CdTe layer (2) and the PbTe layer (3) It is a naturally formed two-dimensional electron gas (5), and the two-dimensional electron gas (5) is in ohmic contact with the metal electrode (1). 2 . The novel photoelectric potential-sensitive detector based on a heterojunction two-dimensional electron gas according to claim 1 , wherein the metal electrode ( 1 ) is a Cu electrode. 3 . 3. The novel photoelectric potential-sensitive detector based on heterojunction two-dimensional electron gas according to claim 1, characterized in that, the ohmic contact between the two-dimensional electron gas (5) and the metal electrode (1) , is achieved by diffusing the metal electrode (1) through the CdTe layer (2) by annealing in a vacuum environment. 4. The novel photoelectric potential-sensitive detector based on a heterojunction two-dimensional electron gas according to claim 1, wherein the potential-sensitive detector is based on the lateral photovoltaic effect of the two-dimensional electron gas (5). work. 5 . The novel photoelectric potential-sensitive detector based on a two-dimensional electron gas in a heterojunction according to claim 1 , wherein the photoelectric response of the device is derived from the thick thin-film PbTe layer ( 3 ) in the heterojunction. 6 . 6. a preparation method of the novel photoelectric potential sensitive detector based on heterojunction two-dimensional electron gas as claimed in claim 1 or 2 or 3 or 4 or 5, is characterized in that, its preparation step is as follows: 1) Using the molecular beam epitaxy method, a CdTe layer (2) and a PbTe layer (3) are grown on the BaF ₂ substrate (4), respectively, to form a heterojunction, and the two-dimensional electron gas (5) is at the heterojunction interface. formed naturally; 2) Photolithography metal electrode pattern on the sample; 3) depositing a Cu film with a thickness of 50-200 nm on the photoetched sample by magnetron sputtering or electron beam evaporation, and then peeling it off to shape the metal electrode (1); 4) Place the sample in a vacuum environment and anneal it at 100-200°C for 30-60 minutes and then stop. 7 . The method for preparing a novel photoelectric potential-sensitive detector based on a heterojunction two-dimensional electron gas according to claim 6 , wherein the thickness of the PbTe layer in the step 1) is 1-3 μm, and the thickness of the PbTe layer is 1-3 μm. 8 . The thickness of the CdTe layer is 50-300 nm. 8. The preparation method of a novel photoelectric potential-sensitive detector based on a heterojunction two-dimensional electron gas according to claim 6, wherein in the step 1), the surface concentration of the two-dimensional electron gas at room temperature is about is 1×10 ¹³ cm ⁻² , and the mobility is about 900 cm ² /V·s. 9 . The method for preparing a novel photoelectric potential-sensitive detector based on a heterojunction two-dimensional electron gas according to claim 6 , wherein the size of the effective working area of the detector is 3 mm×3 mm. 10 . 10 . The method for preparing a novel photoelectric potential-sensitive detector based on a heterojunction two-dimensional electron gas according to claim 6 , wherein in the step 4), the ambient air pressure for annealing is lower than 5×10 ⁻⁴ . Pa, annealing temperature and annealing time were 100-200°C and 30-60min, respectively.

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