Investigation of the Trap States in Fully-Recessed Normally off LPCVD-Si3N4/PEALD-AlN/GaN MIS-HEMT with in-Situ N2 or H2/N2 Plasma Pretreatment

Fully recessed normally off LPCVD-Si3N4/PEALD-AlN/GaN MIS-HEMTs are fabricated with self-terminating wet etch technique. The effects of in-situ N2 or H2/N2 plasma treatments prior to the deposition of PEALD-AlN on the trap states of the device are studied. The interface trap density(Dit) is extracted using the multi-frequency capacitance-voltage (MFCV) method, whereas the border trap density (Nt) is extracted using the low frequency noise (1/f noise) method. The total Dit of devices with in-situ N2 and H2/N2 plasma pretreatment are 9.86 × 10
¹²
and 8.51 × 10
¹²
eV
^-1
cm
^-2
, respectively, an order of magnitude lower than no plasma pretreatment (1.52 × 10
¹³
eV
^-1
cm
^-2
). The Nt of devices with no plasma pretreatment, in-situ N2 and H2/N2 plasma pretreatment are 6.20 × 10
¹⁹
∼ 7.26 × 10
¹⁹
, 5.04 × 10
¹⁸
∼ 7.97 × 10
¹⁸
and 3.05 × 10
¹⁸
∼ 4.06 × 10
¹⁸
eV
^-1
cm
^-3
, respectively. These results indicate that the in-situ H2/N2 plasma pretreatment is more effective at reducing the trap density compared to in-situ N2 plasma pretreatment. Besides, it is found that the plasma pretreatment process may suppress border trap better than interface trap.