Photocurrent analysis of quantum cascade detectors by magnetotransport

Abstract

Photocurrent measurements have been performed on a quantum cascade detector structure under strong magnetic field B applied parallel to the growth axis. The photocurrent shows oscillations as a function of B. In order to describe this behavior, we have developed a rate equation model. The interpretation of the experimental data supports the idea that an elastic scattering contribution plays a central role in the behavior of these structures. We present a calculation of the electron lifetime versus magnetic field which suggests that impurities scattering in the active region is the limiting factor. These experiments lead to a better understanding of these complex structures and identify key parameters to optimize them further.

Description of transport mechanisms in a very long wave infrared quantum cascade detector under strong magnetic field

“…This model is a generalization of the previous one presented in Ref. 20. The sheet density n i of level |i is n i = n eq i + x i , where n eq i is the sheet density at equilibrium (no bias applied and without illumination) and x i the sheet density due to photon absorption.…”

“…As mentioned in Ref. 20, three mechanisms are known to be dominant in midinfrared GaAs QCD -ionized impurities, LO-phonon and interface roughness. The calculated scattering rates of these different processes at B = 0 T, T = 0 K and zero voltage are presented in Table II.…”

“…For interface roughness, we used a Gaussian autocorrelation of the roughness with an average height of ∆ = 2.8Å and a correlation length of Λ = 60Å. 20,31 For ionized impurities scattering, we used Ref. 20.…”

“…19 Under illumination, magnetomeasurements of photocurrent in a 8 µm QCD have evidenced the crucial role of ionized impurities in QCD transport properties. 20 In this paper, after describing the QCD structure in Sec. II, we focus on the analysis of dark current as a function of temperature in Sec.…”

Quantum scattering engineering of quantum well infrared photodetectors in the tunneling regime

“…Moreover, we have identified at least two other very common cases where our doping shift method may be applied ͑i͒ first in midinfrared quantum cascade detector, 23,24 the R 0 A ͑product of the resistance of the device under null bias by the area of the pixel͒ value is limited by the electonimpurities scattering, 25 shifting the doping will allow an increase in the R 0 A. ͑ii͒ In bicolor QWIP the operating temperature is generally determined by the longest wavelength device, making that the lowest wavelength device generally has this dark current operating in the tunnel regime.…”