Investigation of traps in AlGaN/GaN HEMTs on silicon substrate

Abstract

PACS 68.55. Ln, 71.55.Eq, 73.20.Hb, 85.30.Tv Deep levels in AlGaN/GaN heterostructures are known to be responsible for trapping processes like current collapse or dispersion. In order to investigate these processes we performed different measurements on HEMTs fabricated with heterostructures grown on silicon substrate. First by photoionization spectroscopy we found three different traps with activation energies of about 2.1 eV, 2.9 eV and 3.2 eV. Secondly, the temperature dependent relaxation of the drain current was investigated by the backgating current deep level transient spectroscopy (DLTS) method. Hereby we detected majority and minority carrier traps in the GaN buffer at the energies E V + 0.41 eV and E C -0.55 eV, respectively. The latter energy can be attributed to the well known "E2" level in GaN.

Investigation of traps in AlGaN/GaN high electron mobility transistors by sub-bandgap optical pumping

“…[1][2][3][4][5][6][7][8][9][10][11][12] Moreover, subsequent electrical stressing of the HEMTs during operation leads to creation of more traps and further device degradation through various mechanisms, including gate contact sinking, shallow trap formations, and the inverse piezoelectric effect. [13][14][15][16] For each of these mechanisms, there is an increase in trap-related device degradation. 1,4,8,[13][14][15][16][17][18][19] To better understand these traps, techniques such as deep-level transient spectroscopy (DLTS), cathodoluminescence, electroluminescence, and photoluminescence (PL) are attractive, and in the latter three cases, they allow probing of the entire bandgap.…”

“…[13][14][15][16] For each of these mechanisms, there is an increase in trap-related device degradation. 1,4,8,[13][14][15][16][17][18][19] To better understand these traps, techniques such as deep-level transient spectroscopy (DLTS), cathodoluminescence, electroluminescence, and photoluminescence (PL) are attractive, and in the latter three cases, they allow probing of the entire bandgap. Carbon-related trap centers in the buffer layer of AlGaN/GaN HEMT structures were found to be located at 0.9-1.3 eV below the conduction band by DLTS, and these affect the breakdown voltage and gate leakage current.…”

An Investigation of Carbon-Doping-Induced Current Collapse in GaN-on-Si High Electron Mobility Transistors

“…Those defects act as deep traps on the GaN surface or in the buffer layers. Some unexpected effects, such as the vertical leakage, reduction in BV, and CC, are strongly presumed to be related to those defects [30,31]. Electrons captured in or escaping from those traps result in destructive phenomena because of the charging/discharging activities in those traps.…”

Storage and release of buffer charge in GaN-on-Si HEMTs investigated by transient measurements

“…9,10) In most cases, dynamic-R DS,ON originates from charge trapping in the buffer (ionization of buffer acceptors, see Refs. [11][12][13]. In several cases, dynamic-R DS,ON has a non-monotonic dependence on trapping voltage, 14,15) showing an increase for moderate voltages, and a decrease for high drain bias.…”