Correlation between E 1 transition broadening and carrier mobility in the channel layer of pseudomorphic high electron mobility transistor epistructures

We present results from photoreflectance (PR) experiments conducted near the E 1 transition energies (2.60–3.35 eV) of Al 0.25 Ga 0.75 As/In 0.15 Ga 0.85 As heterostructures that constitute the upper layers of pseudomorphic high electron mobility transistor (PHEMT) device epistructures. The lifetime broadening parameter (Γ) of the PR signal from the higher lying transition ( E 1 ) of InGaAs layer shows a strong correlation with the electron mobility. The E 1 transition energies of the AlGaAs and InGaAs layers were used to determine the aluminum and indium mole fractions in the alloy. This study provides an insight into the correlation of a PR parameter with a carrier transport property and provides an alternate method to characterize the barrier and channel layers of PHEMT device structures. The results indicate the advantages of PR characterization employing higher lying transitions.