Calculation and photoresponse measurement of the bound-to-continuum infrared absorption in p-type GaAs/${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As quantum wells

The bound-to-continuum linear absorption coefficient in p-type GaAs/${\mathrm{Al}}_{0.3}$ ${\mathrm{Ga}}_{0.7}$As quantum wells is calculated based on the electronic structure, wave functions, and optical matrix elements obtained from an 8×8 envelope-function approximation calculation and then compared to experimental photoresponse measurements on 30-, 35-, and 40-Å-wide wells. The calculation for the bound and continuum states proceeds independently, owing to the different boundary conditions satisfied by these states. We eschew the use of an artificial large box to confine the continuum wave functions. Good agreement is obtained between experiment and theory with respect to the shape, relative magnitude, and long-wavelength threshold of the bound-to-continuum spectrum for the three measured samples. For an aluminum content of 30%, the calculated linear absorption coefficient for bound-to-continuum absorption in the 8–12-μm window is optimized for the well width of 45 Å due to the presence of a resonant LH2 (second light-hole) state at the top of the well.