LPE Growth And Device Fabrication Of InAsSb Medium-wave Infrared Detector At Room Temperature

Nowadays,the research on improving the operation temperature of photovoltaic narrow-bandgap semiconductor infrared detectors is a major tendency in the development of infrared techniques.III-V group InAs-based semiconductor materials are excellent candidates for the fabrication of HOT?High Operation Temperature?infrared photodetectors.Liquid phase epitaxy?LPE?,which works in a near thermodynamic equilibrium growth mode,is suitable for the growh of perfect crystallinity InAs-based materials.In this work,high quality InAs_0.94Sb_0.06 and InAs_0.89Sb_0.11 absorber materials were obtained by LPE technique,with cut-off wavelength up to 3.9um and 4.4um at room temperature,respectively.InAs_1-x-ySb_xP_y thin films,which work as barrier layer and window layer,were obtained by LPE technique.Then p Bin device structure(p for p-type InAssubstrate,B for p-type InAs_1-x-ySb_xP_y barrier layer,i for unintentionally doped InAs_1-xSb_x absorber layer,n for n-type InAs_1-x-ySb_xP_y window layer)was designed,and its structure,optical and electrical properties were characterized and analyzed.Based on material growth,InAsSb infrared mesa detectors were fabricated,and their performances such as dark current and photoelectric response were tested and analyzed.The main results achieved in this dissertation are summarized as follows:?1?Research on different growth patterns of LPE.Two different growth patterns-step-cooling and super-cooling,were applied in the growth of GaAs_0.9Sb_0.1.Research results showed that compared with super-cooling pattern,step-coolingpattern exhibited slower growth rate,and GaAs_0.9Sb_0.1 epilayer grown by step-cooling exhibited better crystal quality and sharper interface,while there were nosignificant differences on photoluminescence?PL?properties between GaAs_0.9Sb_0.1epilayers grown by two different growth patterns.?2?Research on LPE growth and properties of InAs_1-x-ySb_xP_y epilayers.High qualityInAs_1-x-ySb_xP_y epilayers of different components were grown on InAssubstrates byLPE technique.The components,structures and optical properties of InAs_1-x-ySb_xP_yepilayers were investigated by Rutherford backscattering spectrum?RBS?,Highresolution X-ray diffraction?HRXRD?spectrum and PL spectrum,respectively.Results show that the P component of epilayers could be as high as 0.27,and thecorresponding energy bandgap is 0.48e V at room temperature.The FWMH valuesof the X-ray rocking curves of InAs_1-x-ySb_xP_y epilayers are comparable to that ofInAssubstrate,indicating excellent crystal quality,and the PL spectrum is bright atroom temperature,indicating low recombination defect density.In addition,thesurface morphology of the material was investigated.Results show that there aretwo typical types of defects——“globule”and“hillock”.The morphology of thedefects was characterized by scanning electron microscopy?SEM?,scanning probemicroscopy?SPM?,atomic force microscopy?AFM?and energy dispersive X-rayspectroscopy?EDAX?,and the mechanism of their formation was analyzed.Basedon the research of surface defects,the material growth technology was thenoptimized.?3?Analysis of dark current sources and design of device structure.The dark currentof photodiodes under zero bias or small reverse bias mainly comes from thefollowing aspects:diffusion current that originates from the diffusion of minoritycarriers from both sides of the depletion region,Shockley-Read-Hall?SRH?recombination current that comes from the depletion region and surface leakagecurrent.For InAsSb photodetectors operating at room temperature,diffusioncurrent takes the dominate position when the surface leakage current has beensuppressed.Based on the analysis results of dark current,p Bin detectors weredesigned and fabricated,in which the wide bandgap InAs_1-x-ySb_xP_y barrier layer?Bof the p Bin structure?blocks the diffusion current that comes from the substrate,and the wide bandgap InAs_1-x-ySb_xP_y window layer?n of the p Bin structure?suppresses the surface leakage current by Fermi level pinning.?4?Device fabrication,performance test and analysis.The dark current of detectorswith InAs_0.94Sb_0.06 absorber?response wave band at 2.4-3.9um?was 1.4A/cm²under-100m V bias at room temperature,and the peak detectivity was 1.3×10⁹cm Hz^1/2W^-1 at room temperature and 6.7×10¹⁰cm Hz^1/2W^-1 at 77K,respectively.The dark current of detectors with InAs_0.89Sb_0.11 absorber?response wave band at2.4-4.4um?was 1.7A/cm² under-100m V bias at room temperature,and the peakdetectivity was 1.2×10⁹cm Hz^1/2W^-1 at room temperature and 1.1×10¹⁰cm Hz^1/2W^-1at 77K,respectively.Clear images of the U-shaped heat pipe were obtained atroom temperature using both detectors.?5?Research on passivation of the devices.Effects of different passivation filmsystems such as Al₂O₃?Si₃N₄ and Si O₂,and different deposition techniques on the passivation and antireflection of the devices were investigated.Results showed that by successively depositing 40nm Al₂O₃ using atomic layerdeposition?ALD?and 650nm Si₃N₄ using inductively coupled plasma chemical vapor deposition?ICPCVD?,the brightest PL spectrum?5 times brighter than bare InAssubstrate?and lowest reflectance?1/2 of that of bare InAssubstrate?were obtained.Unfortunately,the dark current of passivated devices wasn'treduced as expected.This is possibly because of poor procession of the interfaces?between the surface of the devices after etching and the passivation layer?indevice fabrication,thus introducing conducting channels at the interfaces.