Epitaxial Optimization of 130-nm Gate-Length InGaAs/InAlAs/InP HEMTs for High-Frequency Applications

In this paper, the influence of epitaxial-layer design on high-frequency properties of 130-nm gate-length InGaAs/ InAlAs/InP high-electron-mobility transistors (InP HEMTs) has been investigated. The In channel content ([In]: 53%, 70%, and 80%), the J-doping concentration (delta: 3, 5, and 7times10¹² cm^-2), and the Schottky-layer thickness (d_SL: 9,11, and 13 nm) have been varied. The maximum frequency of oscillation f_max, the cutoff frequency f_T, the drain-to-source current JDS, and the transconductance g_m have been analyzed for InP HEMTs. All devices exhibited an increase in I_DS with increasing [In], delta, and d_SL. An increase in f_max, f_T, and g_m were observed with increasing [In]. When changing [In] from 53% to 80%, f_T and f_max improved by 14% and 21%, respectively. For the delta parameter, an increase in f_T and g_m. was found. However, f_max was drastically reduced for the highest delta. This is suggested to be due to the formation of a parasitic conduction channel located at the doping plane in the HEMT structure for delta > 6.3 times 10¹² cm^-2. For the d_SL parameter, an optimum with respect to f_max, f_T, and g_m. was observed. The optimized HEMT exhibited an extrinsic f_T and f_max of 250 and 300 GHz, respectively.