甚长波量子阱红外探测器中的双激发态工作机理

通过对甚长波量子阱红外探测器的变温变偏压光谱实验,发现了光电流谱峰值响应波长与半高宽随偏置电压和温度变化均会发生变化,尤其以小偏压下峰值移动明显.结合器件能带结构计算的结果,提出了甚长波量子阱红外探测器中双激发态工作模型,并阐明了其中束缚态-准束缚态跃迁模式中准束缚态的物理特性,包括隧穿特性和热离化特性,以及不同工作条件下这两种物理过程在形成光电流时的主导性.同时,验证了甚长波量子阱红外探测器件的第一激发态随外界工作条件的变化会呈现出准束缚到准连续的变化特性.最后,揭示了在甚长波量子阱红外探测器工作中束缚态-准束缚态跃迁工作模式对于降低器件暗电流、提升器件工作温度、提高器件探测率的有效性.

The working mechanism of the double excited states in the very long wavelength quantum well infrared detector

The temperature-and voltage bias dependent photocurrent spectra of very long wavelength GaAs/AlGaAs quantum well infrared photodetectors were studied by spectroscopic measurements and the corresponding theoretical calculations. It is found that the peak response wavelength will shift with the changing of voltage bias and temperature. With the assistance of band structure calculations, we proposed a model of the double excited states which explains the experimental observations very well. Meanwhile, the working mechanism of the quasi-bound state confined in the quantum well, including the processes of tunneling and thermionic emission, were also investigated in detail. Based on our model, two transition processes, including the ground state to the first excited state transition and the ground state to the continuous state transition have been separated from the photocurrent spectrum. The two normalized photocurrent spectra peak wavelength agreed reasonably well with the calculating results. The results allow a better understanding of bound-to-quasibound state transition and bound-to-quasi-continuous state transition and thus a better optimization of the QWIP performance.