| Summary: | 碩士 === 國立東華大學 === 光電工程研究所 === 97 === Photoluminescence (PL) and photoreflectance (PR) are used to study optical properties of semiconductors. In this work, we characterize InAlAs/InGaAs metamorphic high-electron mobility transistors (MHEMT) with tensile and compressive strain by using PL and PR technics. There are two inter-subband transition features of 11H and 21H that can be observed in the compressively-strained MHEMT (CS-MHEMT) sample in the PL spectra. In the case of tensile-strained MHEMT (TS-MHEMT), PL spectra in low temperature, show the splitting of heavy-hole and light--hole bands at the valence-band top in the channel layer of the TS-MHEMT. The three transition features observed from PL include 11H, 21H, and 11L. Particularly, the transition energies of 11H and 21H for both CS and TS MHEMTs are blue shifted from 16 to 80K due to different trends of thermal expansion coefficient of InAlAs and InGaAs. In the TS-MHEMT, the PR spectra also slow Franz–Keldysh oscillations (FKOs) above 0.8eV. By fitting the FKOs of the PR spectra from 180 to 340 K, the built-in electric field of the channel layer increases as the temperature increases.
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