Study On The Optimization And Performance Of P-GaAs Homojunction THz Detectors

This paper mainly focused on the optimization of the structure of p-GaAs THzdetectors. By designing the resonant cavity, higher quantum efficiency was expected.Besides, the comprehensive properties of the corresponding optimized detector werecalculated.In the former part, we elaborated the theoretical methods and models involved in oursimulation. Firstly, on the basis of the comparison on two kinds of calculation methodsabout the light absorption within multilayered medium, the Fresnel coefficient matrixmethod was considered to be an optimal choice. Then, the detection mechanism, thestructure, the work function, the theoretical model of the detecting process, the quantumefficiency, the collision ionization, the dark current and the resonant cavity of thehomojunction work function detectors were comprehensively introduced.In the latter part, considering the effects of parameters like temperature and biasvoltage, quantum efficiencies of detectors with various parameters were simulated. Finally,the quantum efficiency of the resonant cavity enhanced p-GaAs homojunction THzdetector was improved to17%, under optimized materials and structure parameters. In aconventional optimization, there would be an apparent error in their results, since they didnot take the parameters like temperature and bias voltage into consideration. In ouroptimization, a general gold layer was employed as the bottom reflector, and four kinds ofdifferent amplitude reflectivities, phase positions and light intensity reflectors werecomprehensively considered. Finally, a natural interface mirror was selected as the topreflector, for its simplicity in process and high performance. And then, The relationships among the dark current, responsivity and detectivity ofthe detectors which optimized with the parameters we obtained, bias voltage, temperatureand spectral frequency were simulated, leading to an optimized bias voltage range(10-40mV), an optimal temperature (<8K) and a maximum detectivity (4.1×1010cmHz1/2/W). By applying a pair of matched mirrors, the ultimate quantum efficiency, thedetectivity and the responsivity are26%,5.7×1010cm Hz1/2/W and25.9A/W.