基于Ga2O3相结的高性能自供电日盲紫外探测器

Solar-blind ultraviolet photodetector does not sensitive to solar radiation, with the characteristics of high sensitivity and low false alarm rate, has a wide range of applications in military and civilian fields such as the missile tracking, ultraviolet communication, corona monitoring, and so on. Ga2O3, with a band gap of 4.9 eV, is a natural material of solar-blind ultraviolet detection. Recently, there have several reports about solar-blind ultraviolet photodetector based on Ga2O3 materials at home and abroad (including our team). The research results show that the photodetector based on heterojunction can separate the photogenerated carriers quickly and effectively using the junction effect, improve the device performance greatly. However, the heterojunction photodetector also has some disadvantages, such as: the high quality epitaxial film is difficult to obtain (due to the lattice mismatch); photoresponse easily expands to ultraviolet visible area (because the band gap is narrower than Ga2O3), etc. In view of Ga2O3 with the characteristics of various crystal structure and phase transformation, this project puts forward to construct Ga2O3 phase junction (such as: α-Ga2O3/β-Ga2O3, etc.). The small lattice mismatch and similar band gap will solve the above problems which are existed in the heterojunction. And the matched band structure at the interface of phase junction will promote the carrier separation and improve device performance. The Ga2O3 solar-blind ultraviolet photodetector based on phase junction has a self-powered characteristic. This project will explore the phase formation rule of Ga2O3 material, construct the phase junction, study the charge transport mechanism, and manufacture the high-performance Ga2O3 based solar-blind ultraviolet photodetector.

日盲紫外探测器不受太阳光影响，具有灵敏度高、虚警率低等特点，在导弹跟踪、紫外通信、电晕监测等军民领域有广泛的应用。Ga2O3带隙约为4.9 eV，是天然的日盲紫外探测材料，近年来，国内外（包括我们研究组）在基于Ga2O3材料的日盲紫外探测器研究方面已有一些报导。研究表明基于异质结结构的探测器利用结效应能快速、有效地分离光生载流子，极大地提高器件性能，同时却遇到因异质材料晶格与带隙的不匹配导致器件制备及日盲区保持的困难。鉴于Ga2O3具有多种晶型及相变的特点，本项目提出构筑Ga2O3相结结构（如：α-Ga2O3/β-Ga2O3），较小的晶格失配度和接近的带隙将解决异质结中存在的问题，相结界面处匹配的能带结构将促进载流子快速分离，同时基于该结构的探测器将伴有自供电的特性。本项目将探索Ga2O3材料的成相规律，构筑相结并深入研究电荷的传输机制，制备高性能的Ga2O3基日盲紫外探测器。

日盲紫外探测器因不受太阳光背景影响，具有灵敏度高、虚警率低的特点，在日盲紫外通信、导弹预警跟踪等军用领域，以及在生物医疗(如：杀菌消毒紫外线强度检测)、高压电晕探测、臭氧层空洞监察等民用领域具有广泛应用。Ga2O3的禁带宽度为4.90eV，处于日盲区(200-280nm)，同时具有极高的化学稳定性和热稳定性，是天然的日盲紫外探测材料。器件节能化和小型化的发展趋势要求我们制备自供电型的探测器。Ga2O3有多种晶相，合适的两种晶相构成的相结在界面处能形成第二类型的能带排列，即某相的导带与价带位置均比另一相要高，能实现光生载流子快速、有效地分离。本项目针对获得高性能的Ga2O3基自供电探测器为目标开展了一系列工作，取得了如下成果：1）Ga2O3α/β相结的构筑与包覆层厚度调控。通过高温快速热处理的方式在α-Ga2O3纳米柱表面原位形成β-Ga2O3包覆层，构筑高质量的β-Ga2O3/α-Ga2O3相结，通过控制退火温度、退火时间等参数精确实现对β-Ga2O3包覆层厚度的调节；2）基于α/β相结Ga2O3的自供电日盲紫外探测器。制备了基于β-Ga2O3/α-Ga2O3相结的固态型和光电化学型自供电日盲探测器，均表现出优异的日盲光电特性，其中固态型探测器在0V时的抑制比(R254nm/R365nm)为2.7×10^3；3）Ga2O3的亚稳相获得与薄膜外延生长技术。首次采用PECVD方法在较低温度下（820℃）实现高速率（0.58μm/h）、低成本择优生长。并通过Cu、Mn、Al掺杂获得了γ亚稳相薄膜，通过Sn掺杂制备了ε相薄膜，搞清了相转变规律；4）基于异质结、pn结的高性能自供电日盲紫外探测器。我们制备获得的Sn:Ga2O3基探测器在0V偏压下对254nm光响应高达3.05A/W，为目前报道的最高值，探测率为1.69×10^13cm·Hz1/2·W-1，器件展现出灵敏度高、响应速度快的特性。通过本项目的研究，我们理清了Ga2O3不同晶型之间的转化规律，完成了对Ga2O3相结的可控构筑与探测器制备，获得了高性能的相结自供电探测器，并拓展到Ga2O3基异质结自供电探测器的研究。同时，我们也取得了丰硕的科研成果，在国际知名期刊发表SCI论文27篇（其中一作4篇，通讯19篇），申请专利14个（已授权8个），指导或联合指导研究生12名。