基于Ga2O3/MgZnO扩散增强掺杂pn结的日盲紫外雪崩探测器研究

Solid solarblind UV detection shows brilliant prospects in missile warning, secret comunication and corona discharge monitoring, etc. Avalanche multiplication has been proved to be an effectual way to detect weak signals, which needs a strong electric field area based on pn junction. However, high efficient p-type doping of wide bandgap semiconductors is still a problem. In this project, a p-β-Ga2O3/n-MgZnO heterojunction will be used as the multiplicaton area of an avalanche UV photodiode. The host atoms in each layer are just the desired dopant for the neighboring layer. Therefore, thermal diffusion at interface is not a degradation factor for the pn junction any long, but the enhancement factor for doping each layer.It will enhance the junction electric field by diffusion into each other at the junction interface, (i.e.enhancing p-doping of Ga2O3 by Mg and Zn diffusion into the β-Ga2O3 layer, and enhancing n-doping of MgZnO by Ga diffusion into the MgZnO layer.) It is very beneficial to p-typed doping for wide bandgap semiconductor. The strong electric field is advantageous to the multification of carriers in an avalanche photodiode. In this project, we will optimize the p-type doping of β-Ga2O3, control the interface diffusion, and study the carrier transport in every layer and interface of the multilayered structure. The end goal is realizing solar blind avalance photodiode based on MgZnO/β-Ga2O3 heterostructure. Simultaneously, it can also provide a new route for realizing optoelctronics devices based on oxides pn junction.

全固态日盲紫外探测在导弹预警、保密通讯和电晕检测等领域具有广泛应用。雪崩倍增是弱光探测自放大的有效途径，但同时也对材料载流子调控提出了更高的要求。MgZnO，Ga2O3等宽禁带半导体是理想的日盲紫外探测材料，但高效率p型掺杂一直是宽禁带半导体研究的难点。针对上述难题，本项目提出利用p-β-Ga2O3/n-MgZnO构成pn结，并通过Mg、Zn扩散增强Ga2O3的受主掺杂，Ga扩散增强MgZnO的施主掺杂，在界面形成重掺杂pn结，做为雪崩探测器的倍增区。在该互扩散增强掺杂的异质pn结中，热扩散从不利因素转变为结电场增强因素，这对降低工作电压和提高增益是极为有利的。本项目将优化Ga2O3的p型掺杂，研究扩散过程对pn结特性的影响机制以及载流子在器件各界面处的输运特性，最终实现基于Ga2O3/MgZnO异质pn结的日盲紫外雪崩探测器。同时为基于pn结的全氧化物宽禁带半导体器件提供新的实现途径。

全固态日盲紫外探测在导弹预警、保密通讯和电晕检测等领域具有广泛应用。雪崩倍增是弱光探测自放大的有效途径，但同时也对材料载流子调控提出了更高的要求。MgZnO，Ga2O3等宽禁带半导体是理想的日盲紫外探测材料，但高效率p型掺杂一直是宽禁带半导体研究的难点。针对上述难题，本项目提出利用p-β-Ga2O3/n-MgZnO构成pn结，并通过Mg、Zn扩散增强Ga2O3的受主掺杂，Ga扩散增强MgZnO的施主掺杂，在界面形成重掺杂pn结，做为雪崩探测器的倍增区。本项目从高质量beta相Ga2O3薄膜的生长入手，研究Zn、Mg对Ga2O3的受主掺杂作用，研究扩散过程对β-Ga2O3/MgZnO异质结构结晶的影响，期望实现基于Ga2O3/MgZnO异质pn结的日盲紫外雪崩探测器。本项目实现了蓝宝石衬底上201择优取向的单一beta相β-Ga2O3薄膜，锌掺杂的p型Ga2O3薄膜，空穴浓度达到10的16次方；获得了254nm汞灯辐照下具有接近10的7次方的开关比；254/365nm抑制比大于400；实现了Ga掺杂的MgZnO降阻，发现Ga能级随Mg增加变深；实现了ZnO/Ga2O3 微米线紫外雪崩探测器，-6V偏压下响应度1300A/W。实现了ZnO/Ga2O3 异质结pn结，获得了零偏压下紫外光响应，响应速率在十微秒量级，零伏响应度接近mA/w量级。综上，本项目初步实现了高开关比Ga2O3基日盲紫外探测器件，获得了p-β-Ga2O3/n-ZnO零偏压的快速响应紫外光电器件，实现了基于β-Ga2O3/ZnO同轴微米线的日盲紫外雪崩探测器，10V偏压下增益高达29000。但是，由于p型Ga2O3薄膜的空穴浓度未能突破10 的17次方，高效率p型掺杂这一国际性难题没有解决，导致薄膜型pn结雪崩倍增效应还没有观测到，这是一个值得继续攻关的科学课题。