AlGaN異質結雪崩光電二極管的結構設計與制備
發(fā)布時間：2019-05-12 09:55
【摘要】：紫外探測器是國防預警與跟蹤、環(huán)境監(jiān)測、電力工業(yè)以及生命科學等領域所急需的關鍵部件。與現有真空紫外探測器件相比,基于半導體材料的固態(tài)紫外探測器件具有體重小、功耗低、量子效率高、和便于集成等系列優(yōu)勢。其中,寬禁帶Ⅲ族氮化物半導體材料體系中的AlGaN材料,其帶寬可以由3.4eV一直連續(xù)變化到6.2eV,覆蓋日盲波段,是制備深紫外探測器件的優(yōu)選材料。由于高晶體質量的高A1組分AlGaN材料制備困難,面臨著材料缺陷密度較高、p型摻雜效率低等問題,且載流子離化系數隨A1組分升高而逐漸降低等,所以采用普通的雪崩光電探測器(APD)結構和工藝難以制備出高增益的AlGaNAPD器件。為了提高AlGaN APD的性能,本論文在傳統(tǒng)的SAM結構基礎上進行了改進和優(yōu)化,利用低Al組分AlGaN離化系數較高的特點,采用異質結倍增層的結構設計,并引入三臺面工藝和光電化學處理等工藝,成功制備出了高性能的AlGaN雪崩探測器。主要研究內容和結果如下：1.首次提出了異質結增強型AlGaN APD結構,利用低A1組分AlGaN的離化系數較高的特點,在傳統(tǒng)的單一組分的高A1組分Al0.45Ga0.55N倍增層中引入了一層A1組分相對較低的Al0.3Ga0.7N構成異質結構倍增層,以提高APD器件的平均離化系數。模擬結果顯示低A1組分層的組分對器件整體性能有很大的影響,但低A1組分層的使用可能導致器件失去日盲特性。為了兼顧器件的日盲特性,我們在襯底和器件結構之間設計了一個Al0.5Ga0.5N/AlN的分布式布拉格反射鏡(DBR)結構來保證器件日盲特性。倍增層低A1組分和DBR高反區(qū)帶寬折衷結果表明當低A1組分層Al組分為0.3時,能得到性能較優(yōu)的日盲紫外探測器。對比傳統(tǒng)結構,異質結增強結構APD的擊穿電壓下降大約2.5 V,而倍增因子則從傳統(tǒng)結構的7.13×104提高到1.14×105,提升了大約60%。2.發(fā)展了一種雪崩倍增層電場分布精細調控技術,提出通過在異質結倍增層中間插入一層n型AlGaN來實現倍增層電場分布的調控。模擬結果顯示n型AlGaN插入層中摻雜濃度與厚度、A1組分以及異質結的厚度分配比對器件整體性能有重要影響。最后發(fā)現,當插入層AlGaN組分為0.2、厚度為20nm、濃度為1×1017/cm3且低A1組分層的厚度在40nm(總倍增層厚度為200nm)時,器件綜合性能達到最優(yōu),相比調控前的異質結倍增層結構,擊穿電壓降低了2.1V,雪崩增益提高了約53%。3.采用異質結倍增層的結構設計并制備了高增益的AlGaN異質結深紫外雪崩探測器,所制備的器件增益達到了105量級。另外,在器件制備過程中發(fā)展了一系列新的工藝諸如光電化學處理、三臺面結構等關鍵工藝,這些工藝對降低器件漏電流具有重要作用。
[Abstract]:UV detector is an urgent key component in the fields of national defense early warning and tracking, environmental monitoring, power industry and life science. Compared with the existing vacuum ultraviolet detector, the solid-state ultraviolet detector based on semiconductor materials has many advantages, such as low weight, low power consumption, high quantum efficiency and easy integration. Among them, the bandwidth of AlGaN materials in the wide band gap group III nitride semiconductor system can be continuously changed from 3.4eV to 6.2 EV, which covers the diurnal blind band and is the preferred material for the preparation of deep ultraviolet detection devices. Because of the difficulty of preparing high A1 component AlGaN with high crystal quality, the defect density of the material is high, the p-type doping efficiency is low, and the carrier ionization coefficient decreases gradually with the increase of A1 component. Therefore, it is difficult to fabricate high gain AlGaNAPD devices by using ordinary avalanche photodetector (APD) structure and process. In order to improve the performance of AlGaN APD, this paper improves and optimizes the traditional SAM structure, takes advantage of the high ionization coefficient of low Al component AlGaN, and adopts the structure design of heterojunction doubling layer. A high performance AlGaN avalanche detector was successfully fabricated by introducing three-stage process and photoelectrochemical treatment. The main research contents and results are as follows: 1. The heterojunction enhanced AlGaN APD structure is proposed for the first time, which makes use of the high ionization coefficient of low A1 component AlGaN. In order to improve the average ionization coefficient of APD devices, a layer of Al0.3Ga0.7N with relatively low A1 component is introduced into the traditional single component high A1 component Al0.45Ga0.55N multiplier layer to form a heterogeneous doubling layer. The simulation results show that the composition of the low A1 layer has a great influence on the overall performance of the device, but the use of the low A1 stratification may cause the device to lose the diurnal blindness characteristic. In order to take into account the diurnal blindness of the device, a distributed Bragg reflector (DBR) structure of Al0.5Ga0.5N/AlN is designed between the substrate and the device structure to guarantee the diurnal blindness of the device. The results of bandwidth tradeoff between double layer low A1 component and DBR high inversion region show that the better performance of diurnal blind ultraviolet detector can be obtained when the ratio of low A1 layered Al component is 0.3. Compared with the traditional structure, the breakdown voltage of the heterojunction enhanced structure APD decreases by about 2.5V, while the multiplier factor increases from 7.13 脳 104 to 1.14 脳 105, which is about 60% higher than that of the traditional structure. A fine regulation technique for electric field distribution in avalanche doubling layer is developed. It is proposed that a layer of n-type AlGaN be inserted in the middle of double layer of heterojunction to realize the regulation of electric field distribution in multiplying layer. The simulation results show that the doping concentration and thickness, the A1 component and the thickness distribution of heterojunction in the n-type AlGaN insertion layer have an important effect on the overall performance of the device. Finally, it is found that when the AlGaN component of the insertion layer is 0.2, the thickness is 20 nm, the concentration is 1 脳 1017/cm3 and the thickness of the low A1 layer is in the 40nm (total doubling layer thickness is 200nm), the overall performance of the device is the best, which is better than that of the heterojunction double layer structure before the control. The breakdown voltage is reduced by 2.1 V, and the avalanche gain is increased by about 53%. A high gain AlGaN heterojunction deep ultraviolet avalanche detector is designed and fabricated by using the structure of heterojunction doubling layer. The gain of the device is up to the order of 105. In addition, a series of new processes have been developed in the process of device fabrication, such as optoelectronic chemical treatment, three-stage structure and other key processes, which play an important role in reducing the leakage current of the device.
【學位授予單位】：南京大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN312.7
[Abstract]:UV detector is an urgent key component in the fields of national defense early warning and tracking, environmental monitoring, power industry and life science. Compared with the existing vacuum ultraviolet detector, the solid-state ultraviolet detector based on semiconductor materials has many advantages, such as low weight, low power consumption, high quantum efficiency and easy integration. Among them, the bandwidth of AlGaN materials in the wide band gap group III nitride semiconductor system can be continuously changed from 3.4eV to 6.2 EV, which covers the diurnal blind band and is the preferred material for the preparation of deep ultraviolet detection devices. Because of the difficulty of preparing high A1 component AlGaN with high crystal quality, the defect density of the material is high, the p-type doping efficiency is low, and the carrier ionization coefficient decreases gradually with the increase of A1 component. Therefore, it is difficult to fabricate high gain AlGaNAPD devices by using ordinary avalanche photodetector (APD) structure and process. In order to improve the performance of AlGaN APD, this paper improves and optimizes the traditional SAM structure, takes advantage of the high ionization coefficient of low Al component AlGaN, and adopts the structure design of heterojunction doubling layer. A high performance AlGaN avalanche detector was successfully fabricated by introducing three-stage process and photoelectrochemical treatment. The main research contents and results are as follows: 1. The heterojunction enhanced AlGaN APD structure is proposed for the first time, which makes use of the high ionization coefficient of low A1 component AlGaN. In order to improve the average ionization coefficient of APD devices, a layer of Al0.3Ga0.7N with relatively low A1 component is introduced into the traditional single component high A1 component Al0.45Ga0.55N multiplier layer to form a heterogeneous doubling layer. The simulation results show that the composition of the low A1 layer has a great influence on the overall performance of the device, but the use of the low A1 stratification may cause the device to lose the diurnal blindness characteristic. In order to take into account the diurnal blindness of the device, a distributed Bragg reflector (DBR) structure of Al0.5Ga0.5N/AlN is designed between the substrate and the device structure to guarantee the diurnal blindness of the device. The results of bandwidth tradeoff between double layer low A1 component and DBR high inversion region show that the better performance of diurnal blind ultraviolet detector can be obtained when the ratio of low A1 layered Al component is 0.3. Compared with the traditional structure, the breakdown voltage of the heterojunction enhanced structure APD decreases by about 2.5V, while the multiplier factor increases from 7.13 脳 104 to 1.14 脳 105, which is about 60% higher than that of the traditional structure. A fine regulation technique for electric field distribution in avalanche doubling layer is developed. It is proposed that a layer of n-type AlGaN be inserted in the middle of double layer of heterojunction to realize the regulation of electric field distribution in multiplying layer. The simulation results show that the doping concentration and thickness, the A1 component and the thickness distribution of heterojunction in the n-type AlGaN insertion layer have an important effect on the overall performance of the device. Finally, it is found that when the AlGaN component of the insertion layer is 0.2, the thickness is 20 nm, the concentration is 1 脳 1017/cm3 and the thickness of the low A1 layer is in the 40nm (total doubling layer thickness is 200nm), the overall performance of the device is the best, which is better than that of the heterojunction double layer structure before the control. The breakdown voltage is reduced by 2.1 V, and the avalanche gain is increased by about 53%. A high gain AlGaN heterojunction deep ultraviolet avalanche detector is designed and fabricated by using the structure of heterojunction doubling layer. The gain of the device is up to the order of 105. In addition, a series of new processes have been developed in the process of device fabrication, such as optoelectronic chemical treatment, three-stage structure and other key processes, which play an important role in reducing the leakage current of the device.
【學位授予單位】：南京大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TN312.7
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