摘
要
中波红外光电探测技术在航空航天，军事国防，医疗卫生等多个行业有着广泛的应用，其在红外侦查，预警，导弹防御等军事装备领域收到了国际严格管控限制。近年来，红外光电探测技术的水平正逐步提高，应用范围和场景也日益扩大，所以对于红外探测器综合性能的要求也越来越高，探测率更高、响应速度更快，探测识别的波段范围更广等成为目前主要研究目标。为了实现这一目标，红外光电探测器发展到目前已经经历了三代。传统的红外光电材料如 PbS、PtSi、InSb 等难以实现波长范围的拓展，而 QWIPs 由于子带间跃迁机理导致吸收效率低，目前最成熟的 HgCdTe 在吸收光谱向甚长波红外波段拓展时也遇到很大困难。锑化物半导体具有窄带隙能带特性，其结构设计灵活，近年来外延生长技术获得突破，是中红外波段光电器件的理想选择。所以目前国际上正快速发展锑化物这一材料体系，更是以其中 6.1Å 为重点，除去各种二元三元或者多元化合物，还发展了各种低维微纳结构 II 类超晶格材料。但是由于传统 pin 结构光电探测器本身物理机制的限制，导致其器件暗电流水平有一个限制。所以现在人们很多时候不止在研究新型材料，还在研究新型器件结构来降低器件噪声，提高器件性能。2006 年，nBn 单势垒新型探测器作为其中一种可以抑制器件暗电流的探测器类型被提出。这类新型探测器是采用增加宽禁带势垒的方法来抑制探测器 GR 暗电流从而提高器件综合性能。本论文主要是利用先进的分子束外延技术实现高可重复性高质量的材料外延生长并进行相关器件制备，得到高质量高性能的 InAsSb nBn 结构中波光电探测器，主要研究内容以及成果如下：
（1）系统深入的研究了 GaSb 以及 InAsSb，AlAsSb 等化合物的分子束外延的条件，优化了生长温度，V 族元素比例，V/III 族元素比例等生长参数，成功将材料的晶格应变控制在约 400ppm（50arcsec）以内，原子力显微镜（AFM）图像数据 RMS 粗糙度<2Å，X 射线各材料的半峰宽控制在 40arcsec 以内。
（2）从暗电流成分方面研究了 nBn 结构与 pin 结构在暗电流方面的不同，深入了解了 nBn 结构由于引入宽禁带势垒层而带来了可以抑制 GR 暗电流这一优势，而 GR 暗电流是 pin 结构红外光电探测器在低温下暗电流的主要组成部分。
II
（3）成功研制了 InAsSb nBn 结构中波红外光电探测器单元器件，在-0.2V 偏压下，量子效率能够达到 60%以上，300K 时探测器的探测率可以到 109
cmHz 1/2 /W 量级以上。通过变温 I-V 曲线发现在低于 180K 时，pin 器件中 GR 暗电流逐渐超过扩散电流从而成为主要成分，而 nBn 单势垒结构红外光电探测器中 GR 暗电流得到了很好的抑制，起到了理论模型中 nBn 结构应有的优势。
关键词：中波红外, 分子束外延，nBn，光电探测，InAsSb
Abstrate
Abstract There is a wide range of applications for the medwavelength infrared (MWIR) detection technology in defense and military, aerospace, civil, medical and health fields. It has received strict international control restrictions in the field of infrared detection, early warning, missile defense and other military equipment. In recent years, the level of infrared photoelectronic detection technology is gradually improving, and the application range and scenes are also expanding. The requirements for the comprehensive performance of infrared detectors are becoming higher, so the higher detection rate, the faster response speed and the wider detection and recognition band scope has become the main research goal at present. To achieve this goal, infrared detectors have been developed for three generations. Traditional infrared photoelectronic materials such as PbS, PtSi, InSb, etc. are difficult to extend the wavelength range, and QWIPs have low absorption efficiency due to the sub-band transition mechanism. At present, the most mature material HgCdTe is also encountered great difficulty when the absorption spectrum is extended to the very long wavelength infrared. Antimonide semiconductors have the characteristics of narrow gap energy bands and flexible structural design. In recent years, molecular beam epitaxy technology has achieved breakthroughs and become an ideal choice for mid-infrared photoelectronic devices. Therefore, the antimonide material system is rapidly developing, focusing on 6.1Å among them. In addition to various binary or ternary compounds, various type II superlattice materials have also been developed. However, there is a limit to its dark current level due to the limitations of the traditional pin structure photodetector. People research not only new materials, but also new device structures to reduce device noise and improve device performance. In 2006, nBn single barrier structure was proposed as one of the detector structures to reduce the dark current of the detector. This structure type detector mainly improves the device
IV
detection performance by adding a wide band gap barrier layer to suppress the GR dark current of the device. The work of this paper is mainly to use molecular beam epitaxy technology to achieve high quality material epitaxial growth and device preparation, to obtain high-quality high-performance InAsSb nBn structure medwavelength photoelectronic detector. The main research contents and progress are as follows: (1)We thoroughly studied the conditions of molecular beam epitaxy of GaSb, InAsSb, AlAsSb, and optimized the growth parameters such as growth temperature, group V element ratio, and V / III element ratio.We successfully controlled the lattice strain of the material to about 400ppm (50arcsec), and the root-mean-square roughness of the atomic force microscope image data is less than 2Å. In addition, the peak width at half height of each X-ray material is controlled within 40arcsec. (2) The difference in dark current between the nBn structure and the pin structure was studied in terms of dark current composition. We studied the advantage of nBn structure that suppress GR dark current due to the introduction of a wide band gap barrier layer, and GR dark current is the main source of dark current for pin structure photodetectors at low temperature.
(3) We developed the InAsSb nBn structure medwavelength infrared photodetector. Under -0.2V bias, the quantum efficiency can reach more than 60%, and the detection rate of the device reaches more than 10 9
cmHz 1 / 2 /W at 300K. According to the I-V curve at variable temperature, it is found that the GR dark current in the nBn structure device is suppressed, which plays a very good role in in the pin device below 180K. It is the advantage of the nBn structure in the theoretical model .
Key word：MWIR,MBE,nBn, photo-electric detection,
InAsSb
目 录
目
录
第 1 章
红外探测技术概述 -------------------------------- 1 1.1
红外光简述------------------------------------------- 1 1.1.1
电磁波与红外光----------------------------------- 1 1.1.2
黑体辐射----------------------------------------- 2 1.1.3
大气窗口----------------------------------------- 3 1.2
红外探测器------------------------------------------- 4 1.2.1
红外探测器历史----------------------------------- 4 1.2.2
红外探测技术------------------------------------- 8 1.2.3
红外探测的优势及应用---------------------------- 11 1.3
结论------------------------------------------------ 12 第 2 章
nBn 型红外探测器
------------------------------- 13 2.1
nBn 器件结构及原理 ---------------------------------- 13 2.2
nBn 结构的优势 ---------------------------------------- ----------------------------------------------------------- 15 2.3
nBn 器件研究现状 ------------------------------------ 16 2.3.1
InAsSb 器件研究现状 ----------------------------- 16 2.3.2
其他材料 nBn 器件现状---------------------------- 17 2.4
nBn 器件性能参数 ------------------------------------ 18 2.4.1
响应率------------------------------------------ 18 2.4.2
量子效率---------------------------------------- 19 2.4.3
探测器噪声-------------------------------------- 19 2.4.4
噪声等效功率和探测率---------------------------- 20 第 3 章
器件制备及表征方法
---------------------------- 21
3.1
样品的制备------------------------------------------ 21 3.1.1
分子束外延技术---------------------------------- 21 3.1.2
Gen20 MBE 系统 ---------------------------------- 23 3.1.3
MBE 生长校准技术 -------------------------------- 25 3.2
探测器制备工艺-------------------------------------- 27 3.3
外延材料表征方法------------------------------------ 31 3.3.1
高分辨率 X 射线衍射------------------------------ 31 3.3.2
原子力显微镜------------------------------------ 32 3.3.3
透射电子显微镜---------------------------------- 33 3.3.4
光致发光谱-------------------------------------- 34 3.4
单元器件表征方法------------------------------------ 34 3.4.1
低温 I-V 测试系统-------------------------------- 35
VI
3.4.2
光谱响应测试------------------------------------ 35 3.4.3
黑体响应测试系统-------------------------------- 36 第 4 章
nBn 器件外延优化及单元器件性能分析
---------- 37
4.1
GaSb 缓冲层生长 ------------------------------------- 37 4.2
InAsSb 吸收层外延生长 ------------------------------- 38 4.2.1
生长温度优化------------------------------------ 38 4.2.2
V/III 族元素比优化 ------------------------------ 39 4.2.3
V 族元素比例优化 -------------------------------- 40 4.3
AlAsSb 势垒层外延生长 ------------------------------- 41 4.4
器件整体外延生长------------------------------------ 43 4.5
单元器件性能测试与分析------------------------------ 44
4.5.1
I-V 测试及暗电流分析 ---------------------------- 44 4.5.2
量子效率及探测率分析---------------------------- 46 第 5 章
总结和展望----------------------------------------- 51 参考文献--------------------------------------------------- 53 致谢------------------------------------------------------- 59 作者简历及攻读学位期间发表的学术论文与研究成果------------- 60
图标目录
图表目录
图 1.1 电磁波波长-频率的对应关系，以及各电磁波段对应波长 ---------- 2
图 1.2 普朗克黑体辐射定律 ----------------------------------------- 3
图 1.3 红外大气窗口 ----------------------------------------------- 4
图 1.4 红外探测器的发展历史 --------------------------------------- 7
图 1.5 红外光吸收过程 --------------------------------------------- 9
图 2.1 （a）InAsSb nBn 器件结构图 （b）器件能带示意图 ------------- 13 图 2.2 红外探测器不同温度下的暗电流 ------------------------------ 15
图 3.1 MBE 设备生长室结构示意图 ---------------------------------- 21
图 3.2 分子束外延生长表面过程 ------------------------------------ 22
图 3.3 超晶格实验室 Gen20 分子束外延系统 -------------------------- 24 图 3.4 生长速率的测量曲线 ---------------------------------------- 25
图 3.5 InAsSb nBn 器件外延结构简图 ------------------------------- 27
图 3.6 器件工艺流程图 -------------------------------------------- 28 图 3.7 X 射线衍射光路图 ------------------------------------...