Origin and suppression of kink effect in InP high electron mobility transistors at cryogenic temperatures.

The kink effect is a phenomenon that typically occurs in InP-based InAlAs/InGaAs high electron mobility transistors (HEMTs) at cryogenic temperatures. It results in higher output conductance (g_DS) and non-monotonic behavior. This Letter discusses the origin and suppression of the kink effect in InP HEMTs at cryogenic temperatures, which is linked to the structure of gate recess passivation. At room temperature, two devices with different gate recess passivation structures show similar characteristics. However, a temperature-sensitive kink is observed in the non-passivated gate recess structure, leading to the discontinuous transconductance (g_m) and the non-monotonic threshold voltage (V_th) shifts. Based on pulsed and static (non-pulsed) measurement data, surface traps and impact ionization in the high-field region are identified as the origin of the kink effect. Specifically, a positive V_th shift of +160 mV is caused by surface traps when the temperature drops to 150 K. A negative V_th shift of –60 mV is due to the enhanced impact ionization below 150 K. Conversely, the device with a passivated gate recess has a negligible kink effect and effectively improves discontinuous g_m and the non-monotonic V_th shifts (+25 mV) when the temperature drops. Therefore, the device with a passivated gate recess is significant for suppressing the kink effect and maintaining the stability of the device in variable temperature environments. [ABSTRACT FROM AUTHOR]