Photoconductive detector with low power consumption and preparation method thereof

Abstract

The invention discloses a low-power-consumption photoconductive detector and a preparation method thereof, relates to a photoelectric technology, and aims to solve the problems of insufficient balance between high responsivity and low power consumption and the like in the prior art. Comprising an active region semiconductor, a gate dielectric layer and a gate electrode which are sequentially stacked to form a grating effect; one end of the active region semiconductor is provided with a drain electrode, and the other end is provided with a source electrode; the contact between the active region semiconductor and the drain electrode and the contact between the active region semiconductor and the source electrode are Schottky contact. An electron trap is arranged in the gate dielectric layer and is used for absorbing photo-induced electrons generated by the semiconductor in the active region, so that an energy band, far away from the gate dielectric layer, of the semiconductor in the active region moves upwards. The method has the advantages that the dark current is reduced and the light response characteristic is enhanced based on the grating enhancement effect. On-off conversion can be achieved under grid bias, power consumption is reduced, light current and light responsivity are improved, and light detection efficiency is greatly improved.

Description

Technical Field

[0001] The invention relates to photoelectric technology, and in particular to a low-power photoconductive detector and a preparation method thereof. Background Art

[0002] Photodetectors are widely used in the fields of communications, imaging, and sensing, and their performance has an important impact on detection efficiency and energy consumption. At present, common types of photodetectors include photovoltaic detectors and photoconductive detectors. Photovoltaic detectors usually have a lower dark current, but cannot achieve a high gain of photocurrent, which limits their applications in dark light detection and photon counting. Photoconductive detectors have a higher photon gain. For example, the photocurrent gain of silicon-based and germanium-based photoconductive detectors is usually 100 times, so they are favored in applications requiring high responsiveness. However, conventional photoconductive detectors usually require a large operating power, and also face limitations in the light-to-dark current ratio (i.e., the contrast between photocurrent and dark current). In addition, existing photoconductive detectors are limited in gain control, making it difficult to achieve a high light-to-dark current ratio in a high gain state.

[0003] In the prior art, the grating effect has been used in a variety of photodetector structures as a method to enhance the photoelectric response, using electric fields to regulate photogenerated carriers in semiconductors to improve the detector's response. However, these devices often use an ohmic contact structure, which makes it difficult to maintain high photocurrent gain under low dark current conditions. In order to achieve high gain and high responsiveness under low power consumption, innovative designs in detector structure and contact type are required to enhance the effect of photodetection and improve the light-to-dark current ratio, which is suitable for application scenarios such as photon counting that have special requirements for ultra-high photocurrent gain. Summary of the invention

[0004] The object of the present invention is to provide a low-power photoconductive detector and a preparation method thereof, so as to solve the problems existing in the above-mentioned prior art.

[0005] The low-power photoconductive detector described in the present invention comprises an active region semiconductor, a gate dielectric layer and a gate electrode which are stacked in sequence to form a grating effect; a drain electrode is provided at one end of the active region semiconductor and a source electrode is provided at the other end;

[0006] The contacts between the active region semiconductor and the drain and source are all Schottky contacts;

[0007] The gate dielectric layer has electron traps for absorbing photogenerated electrons generated by the active region semiconductor, causing the energy band of the active region semiconductor to move upward away from the gate dielectric layer.

[0008] The bandgap width of the gate dielectric layer is greater than the bandgap width of the active region semiconductor.

[0009] A method for preparing the photoconductive detector comprises the following steps: first preparing a gate; preparing a gate dielectric layer on the gate; preparing an active region semiconductor on the gate dielectric layer and making the width of the active region semiconductor smaller than the gate dielectric layer; preparing a drain at one end of the active region semiconductor, located above the gate dielectric layer, so that the drain forms a Schottky contact with the active region semiconductor; preparing a source at the other end of the active region semiconductor, away from the drain, located above the gate dielectric layer, so that the drain forms a Schottky contact with the source; and introducing defect states to form electron traps when preparing the gate dielectric layer.

[0010] The low-power photoconductive detector and its preparation method described in the present invention have the advantages of reducing dark current and enhancing light response characteristics based on the grating enhancement effect. Under the gate bias, the on and off switching can be realized, the power consumption is reduced, the photocurrent and light response are increased, and the light detection efficiency is greatly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a schematic diagram of the structure of the photoconductive detector described in the present invention.

[0012] Figure 2 yes Figure 1 Schematic diagram of the energy band of the photoconductive detector structure in the X-axis direction.

[0013] Figure 3 yes Figure 1 Schematic diagram of the energy band of the photoconductive detector structure in the Y-axis direction.

[0014] Figure 4 It is a simulation curve diagram of dark current and photocurrent of the photoconductive detector described in the present invention.

[0015] Figure 5 yes Figure 4 Schematic diagram of the energy band relationship at A, B, C, and D.

[0016] Figure 6 It is a simulation curve diagram of the light response of the photoconductive detector described in the present invention.

[0017] Reference numerals:

[0018] 101 drain, 102 active region semiconductor, 130 source, 104 gate dielectric layer, 105 gate;

[0019] a1 drain Fermi level, a2 source Fermi level;

[0020] b1 is the bottom of the semiconductor conduction band in the active region, b2 is the top of the semiconductor valence band in the active region, and b3 is the semiconductor band gap in the active region;

[0021] c1 gate dielectric layer band gap, c2 electron trap;

[0022] d1 gate Fermi level;

[0023] e - Electronics, + Hole. DETAILED DESCRIPTION

[0024] like Figure 1 As shown, a low-power photoconductive detector described in the present invention includes an active region semiconductor 102, a gate dielectric layer 104 and a gate 105 which are stacked in sequence to form a grating effect. A drain 101 is provided at one end of the active region semiconductor 102, and a source 103 is provided at the other end. The contact between the active region semiconductor 102 and the drain 101 and the source 103 is a Schottky contact. The gate dielectric layer 104 has an electron trap for absorbing the photogenerated electrons generated by the active region semiconductor 102, causing the energy band of the active region semiconductor 102 to move up away from the gate dielectric layer 104. The bandgap width of the gate dielectric layer 104 is greater than the bandgap width of the active region semiconductor 102.

[0025] The working principle of the low-power photoconductive detector described in the present invention is as follows:

[0026] When the active semiconductor 102 is illuminated by light, a photocurrent is generated in the source-drain direction under the source-drain voltage.

[0027] like Figure 2 As shown, the relative energy level relationship along the X direction in the drain-active region-source structure is shown, wherein the vertical coordinate E represents energy, and it can be seen that the drain 101 and the source 103 form Schottky contacts with the active region semiconductor 102 respectively.

[0028] like Figure 3 As shown, wherein the horizontal axis E is energy, the energy bands of the active region-gate dielectric layer-gate structure are aligned along the Y direction, wherein the gate dielectric layer 104 has electron traps that can absorb photogenerated electrons generated by the active region semiconductor 102, causing the energy band of the active region semiconductor 102 away from the gate dielectric layer 104 to move upward.

[0029] Figure 4 The gate regulation mechanism of dark current and photocurrent is shown, with an on state and a subthreshold off state. A is the on state of photocurrent, and B is the subthreshold off state of photocurrent. Correspondingly, C is the on state of dark current, and D is the subthreshold off state of dark current. Figure 5 As shown in the figure, for a given parameter example, the Schottky contact formed by the source-drain electrode and the active region has a lower Schottky barrier, which limits the device current to be dominated by hole current, that is, I DSWhen the gate voltage increases toward the positive voltage, the conduction band and valence band of the active region move downward, and the band gap of the active region forms an increasing potential barrier to the source and drain electrodes, hindering the transmission of hole current, so that the photocurrent and dark current of the device decrease. Conversely, when the gate voltage increases toward the negative voltage, the active region energy band moves upward, the barrier between the source and drain decreases, and the device current increases.

[0030] Comparison of photocurrent and dark current: Under illumination conditions, the conduction band and valence band of the active region with the same gate voltage move upward further, because the photogenerated electrons are captured by the electron traps in the gate dielectric layer 104, and form an electric field with the holes in the active region semiconductor 102, raising the energy level of the active layer. This phenomenon causes the width of the Schottky barrier of the source-drain contact to become narrower, and under the tunneling mechanism, the probability of holes transmitting through the Schottky barrier is increased, thereby increasing the hole photocurrent.

[0031] Under no-light conditions, the dark current of the photoconductive detector is regulated by the device gate, and the gate voltage V GS Changing from negative voltage to positive voltage can deplete the carriers in the active area of ​​the device, causing the current to adjust from the on state at point C to the subthreshold off state at point D, maintaining an ultra-low dark current of less than 10fA and achieving a dark current reduction of more than 4 orders of magnitude.

[0032] 514nm laser at 0.01mW / cm 2 Under this condition, the photocurrent of the device increases. The gate voltage V GS Changing from negative voltage to positive voltage can deplete the intrinsic carriers in the active region, but during continuous illumination, the photogenerated carriers cannot be completely depleted, causing the device photocurrent to gradually decrease and then remain constant at a low level.

[0033] like Figure 6 As shown, in the open state, it has 10 5 Excellent responsivity of A / W, with a responsivity of about 500A / W in the low power off state.

[0034] The preparation method of the present invention is used to prepare the photoconductive detector, comprising the following steps:

[0035] First, the gate 105 is prepared. A material with good conductivity, such as metal, metal oxide, conductive organic material, etc. is used, and there is no specific range requirement for its thickness. It can be carried out by using a process method in the prior art such as atomic layer deposition, thermal evaporation, electron beam evaporation, magnetron sputtering, laser pulse deposition, chemical vapor deposition, electroplating, etc.

[0036] A gate dielectric layer 104 is prepared on the gate 105. Generally, an oxide insulator material with a high dielectric constant and a large bandgap is used, and its bandgap is at least larger than the bandgap of the active region material, such as aluminum oxide, hafnium oxide, zirconium oxide, tantalum oxide, etc. It can also be carried out by atomic layer deposition, thermal evaporation, electron beam evaporation, magnetron sputtering, laser pulse deposition, chemical vapor deposition, etc.

[0037] The active region semiconductor 102 is prepared on the gate dielectric layer 104 and the width of the active region semiconductor 102 is smaller than that of the gate dielectric layer 104. The active region material is determined by the wavelength of light required for detection. For example, the bandgap width of the active region semiconductor for detecting the visible light band should be less than 1.6 eV, and the bandgap width of the active region semiconductor for detecting the ultraviolet light band should be less than 3 eV. Optional materials include amorphous silicon, perovskite, two-dimensional materials, organic semiconductors, metal oxides, etc. It can be carried out by existing technical methods such as thermal evaporation, chemical vapor deposition, laser pulse deposition, magnetron sputtering, atomic layer deposition, spin coating, etc.

[0038] At one end of the active semiconductor 102, located above the gate dielectric layer 104, a drain 101 is prepared, so that the drain 101 forms a Schottky contact with the active semiconductor 102. At the other end of the active semiconductor 102, away from the drain 101, located above the gate dielectric layer 104, a source 103 is prepared, so that the drain 101 forms a Schottky contact with the source 103. When preparing the gate dielectric layer 104, defect states are introduced to form electron traps.

[0039] For those skilled in the art, various other corresponding changes and deformations can be made according to the technical solutions and concepts described above, and all of these changes and deformations should fall within the protection scope of the claims of the present invention.

Claims

1. A low-power photoconductive detector, characterized in that: It comprises an active region semiconductor (102), a gate dielectric layer (104) and a gate (105) which are stacked in sequence to form a grating effect; one end of the active region semiconductor (102) is provided with a drain (101), and the other end is provided with a source (103); The contacts between the active region semiconductor (102) and the drain (101) and the source (103) are all Schottky contacts; The gate dielectric layer (104) has an electron trap therein for absorbing photogenerated electrons generated by the active region semiconductor (102), thereby causing the energy band of the active region semiconductor (102) to move upward away from the gate dielectric layer (104).

2. A low-power photoconductive detector according to claim 1, characterized in that: The bandgap width of the gate dielectric layer (104) is greater than the bandgap width of the active region semiconductor (102).

3. A method for preparing the photoconductive detector according to claim 1 or 2, characterized in that: First, a gate electrode (105) is prepared; a gate dielectric layer (104) is prepared on the gate electrode (105); an active region semiconductor (102) is prepared on the gate dielectric layer (104) and the width of the active region semiconductor (102) is smaller than that of the gate dielectric layer (104); a drain electrode (101) is prepared at one end of the active region semiconductor (102) and located above the gate dielectric layer (104), so that the drain electrode (101) and the active region semiconductor (102) form a Schottky contact; a source electrode (103) is prepared at the other end of the active region semiconductor (102) away from the drain electrode (101) and located above the gate dielectric layer (104), so that the drain electrode (101) and the source electrode (103) form a Schottky contact; and when preparing the gate dielectric layer (104), a defect state is introduced to form an electron trap.

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