【作者】 蒋洞微；

【导师】 国凤云；

【作者基本信息】 哈尔滨工业大学 ， 材料工程， 2011， 硕士

【摘要】 近三十年来,红外探测器在军事和民用等方面发展迅速。特别InAs/GaSbⅡ类超晶格显示出优越的性能,其能带结构可调（0～0.8ev）,响应波长范围广,量子效率高,俄歇复合率低以及较小的暗电流,已成为第三代红外焦平面探测器的优选材料。本文研究了具有响应波长可调的InAs/GaInSb超晶格红外探测器,进行了材料生长的优化以及结构表征。并制成光电导单元器件,进而对器件性能进行了研究。主要内容包括:（1）我们使用Riber Compact 21分子束外延设备,在GaAs（100）衬底上外延生长InAs/GaInSbⅡ类超晶格。对材料的生长参数进行了优化,获得较佳的生长温度为:GaAs层600℃,缓冲层（GaSb）520℃,超晶格薄膜（InAs/GaInSb） 390℃。Ⅴ/Ⅲ族束流比:Sb/Ga为3,As/In为10。按照优化后的生长条件,生长了三类样品。1类为InAs/GaInSb（17ML/17ML）×30 , 2类为InAs/GaInSb（17ML/7ML）×30和InAs/GaInSb（7ML/17ML）×30,3类为InAs/GaInSb（7ML/7ML）×30,缓冲层均为0.8μm的GaSb。依据Empirical Tight-Binding Method经验势函数方法设计的响应波长分别为20μm、12μm和8μm。不仅涵盖了8～14μm在军事上有重要应用的大气窗口,而且使响应波段拓展到甚远红外波段,可用于深空探测。利用原子力显微镜（AFM）对外延膜表面形貌观测获得生长后原位退火温度在475℃为佳。利用双晶x射线衍射（DXRD）法和透射电子显微镜（TEM）观测,对材料结构质量进行了表征分析,显示超晶格界面平整、周期厚度均匀、结晶质量较高。所制备样品的超晶格周期厚度依次为10.2nm、7.2nm和4.2nm,Ga1-xInxSb合金层中In的组分为0.2。扫描电子显微镜（SEM）测得材料厚度与成分不均匀性<1.5%。（2）在MBE外延获得高质量超晶格薄膜材料基础上,本论文重点研究了器件光刻工艺、电极制备工艺,成功制作了超晶格台面光电导单元探测器件。器件光刻工艺中刻蚀采用湿法刻蚀,确定了该材料体系最适合的腐蚀系为酒石酸系腐蚀液,其最佳配比为,酒石酸（4g）:H2O2（3.5ml）: HF（1.5ml）:H2O（400ml）。此腐蚀系适合InAs/GaInSb超晶格材料,刻蚀速率容易控制,刻蚀台阶清晰可见,下切效应小。金属电极采用Au-Ni合金,并进行快速退火合金化处理以保证其欧姆接触,退火温度最佳为380℃。此时的I-V特性曲线为线性关系,说明已经很好的合金化。若退火温度过低,电极与材料之间的势垒将使欧姆接触效果不好;若退火温度过高,则将损坏电极,无法达到欧姆接触。理论上探讨了探测器暗电流的机制。（3）论文中对所研制的超晶格台面光电导型单元探测器的探测性能进行了研究。测试分析了超晶格探测器的光电响应状况和探测率D*,分析了超晶格周期厚度对探测波长的影响。利用傅立叶变换红外光谱仪和低温制冷系统,对器件工作温度在10K～77K下红外光电响应谱进行了测量,结果显示1#、2#和3#样品的光谱响应峰值波长分别为16μm、10.8μm、10μm和7.1μm,与设计值相符合。响应波长随超晶格周期厚度的增加而增大,探测器的响应度随着温度的增加而减弱。最后对探测器的探测率进行了测量,计算得到的77K下, 3#器件峰值探测率D*达到1.93×10¹⁰cm·Hz1/2·W^-1。更多还原

【Abstract】 In recent three decades, infrared detectors had a rapid development in military and civilian. Especially, the TapeⅡInAs/GaSb binary superlattice has an excellent material performance such as adjustable energy band structure(0~0.8ev), a wide range of wavelength response, high quantum efficiency, low Auger recombination rate and low dark current that made it the perfect materials for the Third-Generation Infrared Focal Plane Arrays detector.In this work, an adjustable wavelength response infrared detector of InAs/GaInSb SLs has been studied and the growth of SLs has been optimized and the characteristics of materials were examined and analyzed. The photoconductor devices fabrication was completed and the performances of the devices have also been studied. The main results are summarized as follows:(1)We use Riber Compact21 MBE equipment to growth InAs/GaInSb SLs grown on semi-insulating GaAs substrates. Through the optimized parameters we obtain the best temperature for growth: GaAs layer 600℃, the buffer layer (GaSb) 520℃, the SLs layer (InAs/GaInSb) 390℃. TheⅤ/Ⅲbeam ratio: Sb/Ga is 3 and the As/In is 10. According to the optimized condition, we designed three different types of samples that are: InAs/GaInSb (17ML/17ML)×30; InAs/GaInSb (17ML/7ML)×30 and InAs/GaInSb (7ML/17ML)×30; InAs/GaInSb (7ML/7ML)×30. The buffer layers are GaSb for 0.8μm thickness. The designed of response wavelength were 20μm, 12μm and 8μm according to the calculation by Empirical Tight-Binding Method experience potential function. The response wavelengths not only cover the very important atmospheric window in military applications, but also extended to the very long wavelength region that can be used for deep space exploration.We obtained the best in situ postgrowth annealing temperatures of 475℃by using atomic force microscopy (AFM) to observe the epitaxial film surface morphology. The results of DXRD and TEM observation showed that the SLs have an excellent structural quality such as a flat interface, a uniform period thickness and high crystalline quality. The samples’period thicknesses were 10.2nm, 7.2nm and 4.2nm. The value of x in Ga1-xInxSb alloy layer is 0.2. The non-uniformities of thickness and composition were less than 1.5%.(2)In this work, we mainly studied the lithography process of devices and the electrode preparation technology based on the high quality of the SL films and produced superlattice countertops photoconductor unit detectors successfully.Wet etching was used in lithography process of the device and tartaric acid corrosion system was suitable for this material system. The best ingredients are: tartaric acid (4g):H2O2 (3.5ml): HF (1.5ml):H2O (400ml). This corrosion system has a stable etching rate, good etching morphology and longitudinal etching. Au-Ni alloy was used for preparing the metal electrodes. The best annealing temperature is 380℃for ensuring ohmic contact. At this point, the I-V characteristic curve is linear relationship, indicating that the device has been formed for ohmic contact. If the annealing temperature is too low, the barrier between the electrode and materials will lead to bad ohmic contact and if the temperature is too high, it will damage the electrode that the device can not achieve ohmic contact. We theoretically discussed the mechanism of the dark current.(3)In this work, we also have studied the performance of the photoconductor detectors. The spectral response and blackbody tests were carried out at low temperatures. We also analyzed the SLs period thickness’affect on response wavelength.We use the Fourier Transform Infrared Spectroscopy and low temperature refrigeration system to test the spectral response of the devices at 10K to 77K. The results showed that the samples’spectral responses of the peak wavelength were 16μm, 10.8μm, 10μm and 7.1μm. The valve of the peak wavelength was shifted to the longer wavelength with increased the thickness of SL’s thickness and the responsibility of the detector was decreased with increased the temperature. The number 3 device’s peak directivity D* reaches 1.93×1010cm·Hz1/2·W-1 at 77K.更多还原