ISSN:
1089-7550
Source:
AIP Digital Archive
Topics:
Physics
Notes:
We present a simple model for photocurrent spectroscopy of quantum-well p-i-n diodes that provides a quantitatively accurate desciption of the dependence of photocurrent on absorption coefficient and applied bias. The model incorporates the transit-time effect described previously [R. P. Leavitt and J. L. Bradshaw, Appl. Phys. Lett. 59, 2433 (1991)] as a limiting case. It also includes the two major effects of residual background doping in the intrinsic region of the diode: nonuniform electric fields, which affect the transport of carriers, and incomplete depletion at low electric fields, which reduces the amount of photocurrent collected. We show that the background-doping effect alone can mimic the transit-time effects: reduction in the overall carrier collection efficiency, saturation of photocurrent spectral features, and the presence of minima in photocurrent where absorption spectra show maxima. We obtain a closed-form expression for the photocurrent in the general case where both transit-time and background-doping effects are significant. Excellent agreement is obtained between model calculations and experimental room-temperature photocurrent spectra for an 89-period 100-A(ring) GaAs/100-A(ring) Al0.3Ga0.7As multiple-quantum-well diode, where the background doping density, the effective electron mobility, and the built-in potential are treated as adjustable parameters. The background doping density and the built-in potential obtained from the fit are in excellent agreement with independent measurements. We apply the model to predict the dependence of photocurrent on the intrinsic-region thickness of the diode. We also show a dramatic asymmetry between photocurrent spectra measured with light incident from the front and from the back of the diode, and we discuss the impact of this asymmetry on the performance of self-electro-optic-effect devices. We also find good agreement between the model predictions and the photocurrent results of Whitehead et al. [Appl. Phys. Lett. 52, 345 (1988)]. Further, our model qualitatively describes the dependence of the photoluminescence intensity on electric fields in multiple-quantum-well p-i-n diodes.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.356284
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