Analysis of the “Sheet” Charge Concentration at the AIGaN/GaN Interface

In this work reported, the electrical characterization of Al
_0.2
Ga
_0.8
N/GaN interface was analyzed. Characterization of the undoped-Al
_0.2
Ga
_0.8
N/GaN structure provides useful information for power electronics and solar cell device designers. We observed a sheet carrier density of -1.1 × 10
¹³
cm
²
due to the piezoelectrically induced charges present at the Al
_0.2
Ga
_0.8
N/GaN interface. A conduction band offset of 0.27 eV was reported. Ni/AIGaN/GaN rectifying diodes test structure was fabricated, representative of the gate element of heterojunction high electron mobility transistors (HEMT) with annealed ohmic “back contacts”. A drift mobility of ~511 cm
²
/V.s was measured and an ideality factor of 1 indicated that the dominant conduction mechanism is thermionic emission. Electrical measurements on TLM pads test produced a specific contact resistivity of 2.0 × 10
^-3
Ω.cm
²
and a barrier height of -1.1 eV for the rectifying diodes was derived.