MOCVD Growth Of In_xGa_1-xSb/GaSb Heterostructure And Design And Simulation Of The Thermophotovoltaic Cells

InxGa1-xSb, which has unique bandgap properties, is one of theclassic materials in the antimonide system. The bandgap (Eg) ofInxGa1-xSb can be continuously tunable ranging from0.17to0.72eV, andthe responding wavelength covers the mid-infrared air window withwavelength varying from3to5μm. As a consequence, InxGa1-xSbmaterial is widely used in the domain of infrared detection, fibercommunication, navigation and so on. Besides, the InxGa1-xSb/GaSbheterostructure system is the top priority in the fabrication ofphotoelectronic devices such as infrared detector infrared laser, TPV cellsetc. For the advances mentioned above, further study of InxGa1-xSbmaterial and InxGa1-xSb/GaSb heterostructure are imperative. In this work,the preparation of InxGa1-xSb/GaSb heterostructure by MOCVD and theresearch on characters of the epitaxial layer are on the one hand, and onthe other hand, the application of the heterostructure in the field of TPVhas been explored, and an IBTPV cell has been designed and optimizedby Silvaco/TCAD.The study of InxGa1-xSb/GaSb fabricated by MOCVD includes threestages. The first stage is to explore which gas is more appropriatebetween H2and N2in fabrication of InxGa1-xSb/GaSb layer by MOCVD,and experimental result shows H2is much better. The second stage is tostudy the effect of temperature on epitaxy characteristics ofInxGa1-xSb/GaSb layer by XRD, the result shows that the In content in thelayer decreases and crystal quality of layer improves as the temperatureincreases, and the causes are deeply analyzed. Besides, the suitablegrowth temperature ranges from450to500℃, the optimized growth temperature is about480℃. The final stage is to study the effect of gasphase ratio of Ga/III on epitaxy characteristics of InxGa1-xSb/GaSb layerby XRD, the result shows that crystal quality of layer is improved andThe surface morphology is refined with the ratio varying from0.1to0.9,and the causes are explored from the aspects of distribution coefficient ofIn and lattice mismatch.The content of computer simulation contains two parts including thedesign of IBTPV cell and modeling of the designed device.Aimed at device performance reinforcement, the In0.3Ga0.7Sb/GaSbintermediate band thermophotovoltaic (IBTPV) cell is proposed by theincorporation of In0.3Ga0.7Sb/GaSb quantum wells in the i-layer of a GaSbp-i-n thermophotovoltaic (TPV) cell. Based on quantum confinementeffects, the feasible realization of intermediate band is by introducingIn0.3Ga0.7Sb/GaSb quantum wells, and the eigenvalues of quantizedeigenstate in quantum wells can be obtained by solving a Kronig-Pennylike model. The theoretical efficiency of an IBTPV cell is calculated bythe detailed balance model under the blackbody-like thermal sourceradiation spectrum of1300K and the cell temperature at300K. Theefficiency of the optimized In0.3Ga0.7Sb/GaSb IBTPV cell with maximumoutput power density of7W/cm2achieves as high as45.3%, exceedingthe detailed balance single-junction limiting efficiency and exhibiting agreat potential in future application.