AlGaN异质结雪崩光电二极管的结构设计与制备
发布时间：2019-05-12 09:55
【摘要】：紫外探测器是国防预警与跟踪、环境监测、电力工业以及生命科学等领域所急需的关键部件。与现有真空紫外探测器件相比,基于半导体材料的固态紫外探测器件具有体重小、功耗低、量子效率高、和便于集成等系列优势。其中,宽禁带Ⅲ族氮化物半导体材料体系中的AlGaN材料,其带宽可以由3.4eV一直连续变化到6.2eV,覆盖日盲波段,是制备深紫外探测器件的优选材料。由于高晶体质量的高A1组分AlGaN材料制备困难,面临着材料缺陷密度较高、p型掺杂效率低等问题,且载流子离化系数随A1组分升高而逐渐降低等,所以采用普通的雪崩光电探测器(APD)结构和工艺难以制备出高增益的AlGaNAPD器件。为了提高AlGaN APD的性能,本论文在传统的SAM结构基础上进行了改进和优化,利用低Al组分AlGaN离化系数较高的特点,采用异质结倍增层的结构设计,并引入三台面工艺和光电化学处理等工艺,成功制备出了高性能的AlGaN雪崩探测器。主要研究内容和结果如下：1.首次提出了异质结增强型AlGaN APD结构,利用低A1组分AlGaN的离化系数较高的特点,在传统的单一组分的高A1组分Al0.45Ga0.55N倍增层中引入了一层A1组分相对较低的Al0.3Ga0.7N构成异质结构倍增层,以提高APD器件的平均离化系数。模拟结果显示低A1组分层的组分对器件整体性能有很大的影响,但低A1组分层的使用可能导致器件失去日盲特性。为了兼顾器件的日盲特性,我们在衬底和器件结构之间设计了一个Al0.5Ga0.5N/AlN的分布式布拉格反射镜(DBR)结构来保证器件日盲特性。倍增层低A1组分和DBR高反区带宽折衷结果表明当低A1组分层Al组分为0.3时,能得到性能较优的日盲紫外探测器。对比传统结构,异质结增强结构APD的击穿电压下降大约2.5 V,而倍增因子则从传统结构的7.13×104提高到1.14×105,提升了大约60%。2.发展了一种雪崩倍增层电场分布精细调控技术,提出通过在异质结倍增层中间插入一层n型AlGaN来实现倍增层电场分布的调控。模拟结果显示n型AlGaN插入层中掺杂浓度与厚度、A1组分以及异质结的厚度分配比对器件整体性能有重要影响。最后发现,当插入层AlGaN组分为0.2、厚度为20nm、浓度为1×1017/cm3且低A1组分层的厚度在40nm(总倍增层厚度为200nm)时,器件综合性能达到最优,相比调控前的异质结倍增层结构,击穿电压降低了2.1V,雪崩增益提高了约53%。3.采用异质结倍增层的结构设计并制备了高增益的AlGaN异质结深紫外雪崩探测器,所制备的器件增益达到了105量级。另外,在器件制备过程中发展了一系列新的工艺诸如光电化学处理、三台面结构等关键工艺,这些工艺对降低器件漏电流具有重要作用。
[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.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：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.
【学位授予单位】：南京大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN312.7
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