Effects of bias and temperature on the intersubband absorption in very long wavelength GaAs/AlGaAs quantum well infrared photodetectors

Abstract

The temperature- and bias-dependent photocurrent spectra of very long wavelength GaAs/AlGaAs quantum well infrared photodetectors (QWIPs) are studied using spectroscopic measurements and corresponding theoretical calculations. It is found that the peak response wavelength will shift as the bias and temperature change. Aided by band structure calculations, we propose a model of the double excited states and explain the experimental observations very well. In addition, the working mechanisms of the quasi-bound state confined in the quantum well, including the processes of tunneling and thermionic emission, are also investigated in detail. We confirm that the first excited state, which belongs to the quasi-bound state, can be converted into a quasi-continuum state induced by bias and temperature. These obtained results provide a full understanding of the bound-to-quasi-bound state and the bound-to-quasi-continuum state transition, and thus allow for a better optimization of QWIPs performance.

Progress in quantum well and quantum cascade infrared photodetectors in SITP

“…Spectral response curves for samples 522 # and 524 # at different temperatures with a 0.15-V bias. [23] In fact, the normalized photocurrent spectra induced by the intersubband transitions do not change as the temperature and bias change. It is the intensity change of the normalized photocurrent spectra that causes the whole photocurrent spectra to be different at different biases and temperatures as pre-027801-4 sented in Fig.…”

“…units A dashed line is drawn following the peak position as a guide for the eye. [23] Note that with an increase of the bias, the full width at half-maximum (FWHM) ∆λ of the two samples both decreases. The ∆λ /λ (%) of 522 # decreases from 40% at 0.2 V to 15.2% at 0.9 V, while the ∆λ /λ (%) of 524 # decreases from 35% at 0.15 V to 15.4% at 1 V. The obvious change in ∆λ /λ (%) indicates that the transition mode changes as the bias increases.…”

“…In order to illustrate how the different excited states in a QWIP influence its device performance, we designed two typical QWIPs based on the GaAs/Al x Ga 1−x As material system using the BTQB and BTQC, respectively. [23] Two QWIP samples, labeled as 522 # and 524 # were grown on (100)oriented semi-insulating GaAs substrates by means of molecular beam epitaxy. The multiple quantum well (MQW) structure consists of 50 periods of a GaAs well (which is n-doped at 2.5 × 10 17 cm −3 ) and an Al 0.12 Ga 0.88 As barrier.…”

“…Blackbody response of samples 522 # and 524 # at a 500-K source with a chopping frequency of 173 Hz. [23] Wavelength/cm -1 Wavelength/cm -1…”

“…Normalized photocurrent spectra arise from the excitations from the ground state to the first excited state I ph1 (black line) and the ground state to the excited state in the continuum I ph2 (red line). [23] the data above 830 cm −1 in the photocurrent spectra at 0.8 V multiply a factor which is equal to 0.9/0.8 and use the data at 0.9 V to reduce the former result. From this, we get the photocurrent spectrum which is due to the transition from the ground state to the first excited state.…”