Optical characterization of InAlAs/InGaAs metamorphic high-electron mobility transistor structures with tensile and compressive strain

We have measured surface photovoltage (SPV), photoreflectance (PR), and photoluminescence (PL) spectra of two InAlAs/In_xGa _{1 - x}As/InAlAs metamorphic high-electron mobility transistor (MHEMT) structures. One possesses a V-shaped In_xGa_{1 - x}As (x = 0.3-0.5-0.3) tensile-strained channel in In_0.5Al_0.5As/ In_xGa_{1 - x}As/In_0.5Al_0.5As heterostructures, and the other is an In_0.42Al_0.58As/ In_0.53Ga_0.47As/In_0.42Al_0.58As MHEMT structures with In_xGa_{1 - x}As (x = 0.53) compressively-strained channel grown on GaAs by molecular beam epitaxy. The comparison of SPV, PR, and PL spectra facilitates the identification of channel-well transitions in the MHEMT structures with different In _xGa_{1 - x}As channels. Inter-subband transitions, Fermi-level energies, and built-in electric field of the two MHEMT structures with dissimilar In_xGa_{1 - x}As channel are evaluated and discussed from the experimental analyses of SPV, PR and PL measurements. The results showed that the design of tensile-strained MHEMT structure enhances sheet-carrier density and avoids surface-roughness scattering by increasing V-shape electric field between the two channel interfaces. The electron mobility of the tensile-strained MHEMT structure is hence being promoted.