AlGaN/GaN HEMT with LPCVD deposited SiN and PECVD deposited SiCOH low-k passivation

Abstract

This paper reports AlGaN/GaN HEMT with 20 nm LPCVD deposited SiN and 200 nm PECVD deposited SiCOH low-k passivation layer. The capacitance–voltage (C–V) measurement indicates that LPCVD deposited SiN results in a better interface quality compared with the PECVD method. PECVD SiCOH with a dielectric constant lower than 2.2 helps to reduce the parasitic capacitance while providing mechanical support for field plate and protection of passivation layer. The thin and dense LPCVD SiN film passivates the interface. Meanwhile, low-k material results in reduction of CGS + CGD by over 20% and an increased cutoff frequency (fT) compared with SiO2/SiN passivated device.

Fabrication and characterization of AlGaN/GaN HEMTs with high power gain and efficiency at 8 GHz

“…One of the main limiting factors to high performance in GaN HEMTs is the current collapse or DC-to-RF dispersion caused by trapping effects [15,16] . The effects of current collapse can be assessed with PIV measurements.…”

“…As a result, large V DS stress leads to an increase in V K and decrease in I DS . Moreover, with further increase of V DS stress, the current collapse will become more serious [15,16] . According to Eq.…”

“…The 2DEG mobility and concentration are necessary further improved to decrease the access resistances of the HEMT devices [14] . Another important issue is the trap-induced current collapse under high drain voltage bias, which severely degrades the performances of the device at high-frequency operation [15,16] . Although the passivation layer [17] and field plates [18] were introduced to mitigate the trapping effects, the current collapse was still difficult to be eliminated.…”