The Band Offset Of Heterojunction Based On MBJ-CPA Method

In recent years,semiconductor-semiconductor heterojunctions have become increasingly widely used,especially in the fields of photoelectric conversion devices and photocatalysis,such as solar cells,photodetectors,light-emitting diodes,and high-efficiency photocatalysts.The application of solar cells and photocatalyst can effectively improve the energy crisis and environmental pollution problems.As heterojunctions play an increasingly important role and the study of heterojunctions has become increasingly intensive,it is particularly important to design efficient heterojunction.Based on the density functional theory and the Green’s function method,while using the modified Baker-Johnson（MBJ）semi-local exchange correlation functional to obtain the accurate semiconductor band,the band gap of the doped semiconductor alloy is calculated using the coherent potential approximation（CPA）method.Including doped wurtzite structure,perovskite structure and its constituent heterojunction structure.The specific research contents and conclusions are as follows:1.The band gaps of Zn_1-xGa_xO_1-xN_xalloys in the entire concentration range from0 to 1（take a calculated concentration for adjacent to 0.1）and band offsets of the lattice-matched Zn O/Zn_1-xGa_xO_1-xN_xheterojunctions have been studied.The quantitative dependence between band offsets and doped concentrations is obtained.The band gaps of Zn_1-xGa_xO_1-xN_xalloys are found to be adjusted by doped Ga N concentration and exhibit strong band gap bending.By regulating the concentrations of Ga N,Zn_1-xGa_xO_1-xN_xand Zn O can form heterojunctions with type I and type II band offsets.In particular,when in the range 0.81-xGa_xO_1-xN_xcover the visible range,moreover,the Zn O/Zn_1-xGa_xO_1-xN_xform the type II heterojunctions.Devices based on such heterojunction will help to improve the sunlight absorption capacity and improve the carriers collection efficiency.2.The regulation of the band of SrTiO₃by different concentrations of Ba doping and the SrTiO₃/Sr_1-xBa_xTiO₃heterojunctions’properties have been calculated.It is found that the band gaps of Sr_1-xBa_xTiO₃decrease due to the doping of Ba,When the doping concentration is 0.4,the band gap of Sr_1-xBa_xTiO₃will change from indirect to direct band gap;Heterojunctions composed of SrTiO₃and Sr_1-xBa_xTiO₃show type II band offset across the entire range of Ba doping concentrations.