Effect of the spin split-off band on optical absorption in p-type ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$${\mathrm{As}}_{\mathit{y}}$${\mathrm{P}}_{1\mathrm{-}\mathit{y}}$ quantum-well infrared detectors

Experimental investigations of p-type ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$${\mathrm{As}}_{\mathit{y}}$${\mathrm{P}}_{1\mathrm{-}\mathit{y}}$ quantum-well intersubband photodetectors (QWIP’s) led to the discovery of unique features in photoresponse spectra of these devices. In particular, the strong 2–5-μm photoresponse of these QWIP’s was not anticipated based on previous experimental and theoretical results for p-type GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As QWIP’s. Our theoretical modeling of p-type QWIP’s based on the ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$${\mathrm{As}}_{\mathit{y}}$${\mathrm{P}}_{1\mathrm{-}\mathit{y}}$ system revealed that the intense short-wavelength photoresponse was due to a much stronger coupling to the spin-orbit split-off components in the continuum than occurs for GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As QWIP’s. Due to the strong influence of the spin split-off band, an eight-band Kane Hamiltonian was required to accurately model the measured photoresponse spectra. This theoretical model is first applied to a standard p-type GaAs/${\mathrm{Al}}_{0.3}$${\mathrm{Ga}}_{0.7}$As QWIP, and then to a series of GaAs/${\mathrm{Ga}}_{0.51}$${\mathrm{In}}_{0.49}$P, GaAs/${\mathrm{Ga}}_{0.62}$${\mathrm{In}}_{0.38}$${\mathrm{As}}_{0.22}$${\mathrm{P}}_{0.78}$, ${\mathrm{Ga}}_{0.79}$${\mathrm{In}}_{0.21}$${\mathrm{As}}_{0.59}$${\mathrm{P}}_{0.41}$/${\mathrm{Ga}}_{0.51}$${\mathrm{In}}_{0.49}$P, and ${\mathrm{Ga}}_{0.79}$${\mathrm{In}}_{0.21}$${\mathrm{As}}_{0.59}$${\mathrm{P}}_{0.41}$/${\mathrm{Ga}}_{0.62}$${\mathrm{In}}_{0.38}$${\mathrm{As}}_{0.22}$ ${\mathrm{P}}_{0.78}$ QWIP’s. Through this analysis, the insignificance of spin split-off absorption in GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As QWIP’s is verified, as is the dual role of light-hole extended-state and spin split-off hole-extended-state absorption on the spectral shape of ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$${\mathrm{In}}_{\mathit{x}}$${\mathrm{As}}_{\mathit{y}}$${\mathrm{P}}_{1\mathrm{-}\mathit{y}}$ QWIP’s. © 1996 The American Physical Society.