Microwave thermal modulation of photoluminescence in III-V semiconductors

The effects of an applied microwave field on low-temperature photoluminescence (PL) have been investigated in epitaxial ${\mathrm{Ga}}_{0.52}$ ${\mathrm{In}}_{0.48}$P and GaAs. The modulation-frequency dependence of the microwave-modulated PL was compared with the frequency response in nominally identical samples directly heated by an alternating current passing through the sample substrate. We give strong evidence that (1) the mechanism, whereby the microwaves interact with the PL in ${\mathrm{Ga}}_{0.48}$ ${\mathrm{In}}_{0.52}$P, is via simple heating of the lattice and (2) in superfluid helium the time constant for thermal equilibration of the epilayer to its environment is less than 2 μsec, in agreement with theoretical estimates. This thermal-coupling mechanism has been observed in ${\mathrm{Ga}}_{0.52}$ ${\mathrm{In}}_{0.48}$P, ${\mathrm{GaAs}}_{\mathit{x}}$ ${\mathrm{P}}_{1\mathrm{-}\mathit{x}}$, and ${\mathrm{GaAs}}_{1\mathrm{-}\mathit{x}}$ ${\mathrm{Sb}}_{\mathit{x}}$, all of which exhibit a propensity to form ordered structures. The coupling in GaAs, InP, CdS, InP/${\mathrm{Ga}}_{0.47}$ ${\mathrm{In}}_{0.53}$As/InP, and GaAs/${\mathrm{Al}}_{\mathit{x}}$ ${\mathrm{Ga}}_{1\mathrm{-}\mathit{x}}$As/GaAs is not thermal but may involve impact ionization.