In this work, we successfully demonstrated In_0.53Ga_0.47As/InAs/In_0.53Ga_0.47As composite channel metamorphic high electron mobility transistors (mHEMTs) on a GaAs substrate. The fabricated mHEMTs with a 100 nm gate length exhibited excellent DC and logic characteristics such as V_T = −0.13 V, g_m,max = 949 mS/mm, subthreshold swing (SS) = 84 mV/dec, drain-induced barrier lowering (DIBL) = 89 mV/V, and I_on/I_off ratio = 9.8 × 10³ at a drain-source voltage (V_DS) = 0.5 V. In addition, the device exhibited excellent high-frequency characteristics, such as f_T/f_max = 261/304 GHz for the measured result and well-matched modeled f_T/f_max = 258/309 GHz at V_DS = 0.5 V, which is less power consumption compared to other material systems. These high-frequency characteristics are a well-balanced demonstration of f_T and f_max in the mHEMT structure on a GaAs substrate.

We investigated the effect of phase separation on the Schottky barrier height (SBH) of InAlAs layers grown by metal–organic chemical vapor deposition. The phase separation into the In-rich InAlAs column and Al-rich InAlAs column of In_0.52Al_0.48As layers was observed when we grew them at a relatively low temperature of below 600 °C. From the photoluminescence spectrum investigation, we found that the band-gap energy decreased from 1.48 eV for a homogeneous In_0.52Al_0.48As sample to 1.19 eV for a phase-separated In_xAl_1−xAs sample due to the band-gap lowering effect by In-rich In_xAl_1−xAs (x > 0.7) region. From the current density–voltage analysis of the InAlAs Schottky diode, it was confirmed that the phase-separated InAlAs layers showed a lower SBH value of about 240 meV than for the normal InAlAs layers. The reduction in SBH arising from the phase separation of InAlAs layers resulted in the larger leakage current in InAlAs Schottky diodes.

Our investigation focused on assessing the influence of the metamorphic buffer in metamorphic high-electron-mobility transistors (MHEMT) that were grown on GaAs substrates. While an MHEMT exhibited elevated off-state current levels, its direct current (DC) and radio frequency (RF) traits were found to be comparable to those of InP-based lattice-matched high-electron-mobility transistors (LM-HEMTs). However, the Pulsed I–V measurement results confirmed the presence of the fast transient charging effect, leading to a more substantial degradation in drain current observed in MHEMT. In addition, through the low-frequency noise characteristics, it was confirmed that the dominant trapping location was located in the bulk site. The slope of the 1/f noise measurement indicated that the primary trapping site was in proximity to the bulk traps. The carrier-number-fluctuation (CNF) model was employed to extract the bulk trap density (N_t). For the LM-HEMTs, the value was at 3.27 × 10¹⁶ eV⁻¹·cm⁻³, while for the MHEMT, it was 3.56 × 10¹⁷ eV⁻¹·cm⁻³.

In this paper, we reported changes in the growth morphology of n+InAs nanowires (NWs) doped with Te which were selectively grown on nano-hole patterned InP(111)B substrates using an MOCVD method. While the vertical growth of InAs NWs in the direction was extremely suppressed, their lateral growth was enhanced when the diethyl-tellurium (DETe) flow rate was increased as they grew. Moreover, the sidewall planes evolved from ($1\overline{1}0$) (90° against the (111) plane) to a reverse-tapered morphology, which had a 62° slope against the InP (111)B plane, when the Te flow rate and growth time were increased. This indicates that the surfactant effect of adsorbed Te atoms on InAs changes the relative growth rate between (111) and ($1\overline{1}0$) due to the increase in surface free energy in the growth plane.

The structural and electrical characteristics of InGaAs high-electron-mobility transistors regrown on InP metamorphic buffers (MMBs) on GaAs (100) substrates were investigated. Increasing the buffer thickness improved crystalline quality by reducing dislocation density and surface roughness, whereas thinner buffers degraded the two-dimensional electron gas and DC performance. Simultaneous regrowth on conventional InP substrates and MMBs under identical conditions directly assessed the impact of MMB-induced structural defects on device behavior. These findings underscore the importance of strain relaxation and defect control in buffer engineering, providing practical guidance for integrating high-performance III–V devices on lattice-mismatched platforms.