Effect of Electron Irradiation Fluence on InP-Based High Electron Mobility Transistors

In this paper, the effect of electron irradiation fluence on direct current (DC) and radio frequency (RF) of InP-based high electron mobility transistors (HEMTs) was investigated comprehensively. The devices were exposed to a 1 MeV electron beam with varied irradiation fluences from 1 × 10¹⁴ cm^-2, 1 × 10¹⁵ cm^-2, to 1 × 10¹⁶ cm^-2. Both the channel current and transconductance dramatically decreased as the irradiation fluence rose up to 1 × 10¹⁶ cm^-2, whereas the specific channel on-resistance (R_on) exhibited an apparent increasing trend. These changes could be responsible for the reduction of mobility in the channel by the irradiation-induced trap charges. However, the kink effect became weaker with the increase of the electron fluence. Additionally, the current gain cut-off frequency (f_T) and maximum oscillation frequency (f_max) demonstrated a slightly downward trend as the irradiation fluence rose up to 1 × 10¹⁶ cm^-2. The degradation of frequency properties was mainly due to the increase of gate-drain capacitance (C_GD) and the ratio of gate-drain capacitance and gate-source capacitance (C_GD/C_GS). Moreover, the increase of R_on may be another important factor for f_max reduction.