MBE Growth And Property Of Antimonide For Thermophotovotaic Cells

Thermophotovoltaic system has promising applications and commercial value forit’s highly energy utilization, portable and available all-weather. Recently, Researchingon TPV system focus on researching new TPV cells materals, designing device structureand optimizing grow process. Simulation solfware play an important part in suchresearch, such as simulateing convertion efficient at different device structure, differentquality of the crystal and different spectral range, which is a method of significance fordesigning device structure and optimizing grow process. We have designedheterojunction TPV cells with structure of p-GaSb/n-GaAs and p-InAs/n-GaSb. Furthermore, the quality of the crystal has been analyzed by XRD and AFM, theoptical-electrical characteristic was analyzed by I-V testing at last.Firstly, we have simulated the rules of minority carrier recombination lifetime,absorption coefficient, mobility and minority carrier diffusion length changed with thedoping concentration and temperature, which found the theoretical basis for thebehind the simulation.This paper deals with the regularities of convertaion effciency of p-GaSb/n-GaAsPTV cells by PC-1D, it shows that the optimized thickness is0.3μm and the optimizeddoping concentration is10¹⁹cm^-3. Besides, the effect of surface recombination velocityand interface recombination velocity on convertaion effciency were investigate, theresults show that short-circuit current and open-circuit voltages decrease with theincrease of surface recombination velocity and interface recombination velocity. Then, anew TPV cell of p-InAs/n-GaSb was designed, the convertion effciency variations withthickness of InAs layer and doping concentration was simulatied, it shows that theoptimized thickness is0.4μm and the optimized doping concentration is10¹⁹cm^-3.p-GaSb was grown on GaAs as sample one, so do p-InAs/n-GaSb as sample twoand three which are in same structure but different thickness of InAs layer, all of thesesamlpes were grow by MBE. For sample one, the results of AFM show that the filmsare continuous and the RMS roughness is1.98nm, defined as a typical SK growthpattern. The charts of XRD show that the FWHM of sample one is0.140, indicated thegood quality of as grown crystal. For sample two and three, the results of AFM show alow surface roughness that the RMS roughness is1.68nm and1.65nm respectively. Thecharts of XRD show that the FWHM is0.283and0.271respectively which indicated good crystal quality. The thickcess of each sample was measured by AFM aftercorroded by KOH, the results show the thickness of GaSb is0.241μm, and the thethickness of InAs for sample two and three respectively is0.192μm and0.384μm.Finally, we have made the devices by sanding and wet etching method, the voltampere characteristics and I-V curve under illumination were tested by electrochemicalworkstation. The volt ampere characteristics for the sample one illustrate that at thebegining of forward biase, base barrier region current on barrier region, as theincreasing of current injection, it turn to diffusion current. The curve of sample twodidn’t show an inflection point which indicated that there are more defects in these cells.The device made of sample one performanced bad under illumination because of highresistor of substrate, and the I_SC, V_OC, FF respectively are75.5μA,145.70mV and40.57%. For sample two and three, with the increasing of InAs thickness, convertionefficiency turn to be greater, this consistent with the simulation results, and the I_SC, V_OC,FF are98.10mA,266.14mV, FF=46.7%respectively for sample two, and107.551mA，272.14mV, FF=52%respectively for sample three.