Trap‐Related Breakdown and Filamentary Conduction in Carbon Doped GaN

Abstract

A breakdown phenomenon is studied in thin carbon doped GaN layers (GaN:C; carbon concentration 10 19 cm À3 ) embedded between a top metal electrode and bottom n-doped GaN (n-GaN). When slowly sweeping positive bias V at the top electrode up and down, a hysteresis is found with transitions to on-and off-states at voltages V bd;up and V bd;down (<V bd,up ), respectively, and on-to off-current ratios exceeding 10 3 . Breakdown at V bd;up occurs at an electric field of about 0.5 MV cm À1 in GaN:C. For V bd;down < V < V bd;up , transition to on-state is time-dependent with random time-to-breakdown in the ms to 10s range. Electroluminescence measurements in on-state show conduction via multiple standing or slowly moving current filaments (CFs) which number and size increases with total current. The origin of an S-shape I-V curve leading to hysteresis behavior is discussed in terms of trap-related nonlinear generation-recombination processes. Formation of multiple CFs is explained by spontaneous CF formation in a homogeneous spatially extended system composed of an active medium with S-shape I-V curve (here GaN:C) connected in series with a passive layer (here n-GaN). Unlike previous studies in various III-N opto-electronic systems, extended defects are supposed not to be responsible for the CF origin but just for their pinning.

Low Field Vertical Charge Transport in the Channel and Buffer Layers of GaN-on-Si High Electron Mobility Transistors

“…Finally, we note that strong non-linearity can occur in the carbon doped GaN system under some circumstances. Negative differential resistance in the IV characteristics of GaN:C to Si doped GaN diodes [19], and relaxation oscillation behavior in substrate ramp experiments [20], suggest that the transport cannot always be described by band edge transport.…”

“…The key novelty is the recognition that the leakage paths through the UID GaN are non-Ohmic and we propose that this can be explained by the presence of a previously unrecognised diode barrier between the dislocation core and the 2DEG. 19 cm −3 (measured by secondary ion mass spectrometry), 300 nm UID GaN channel, and AlGaN barrier (Fig. 1a).…”

Study of Drain Injected Breakdown Mechanisms in AlGaN/GaN-on-SiC HEMTs

“…2 suggest the presence of a snapback or negative-resistance mechanism associated with the localized transport through the more heavily carbon doped layer. We note that Koller et al [14] have reported negative resistance and a localized breakdown mechanism in carbon doped bulk GaN structures, with associated localized EL light emission. Some of their localized breakdowns were pinned to dislocations, although here the precise nature of the defects is unknown.…”

Investigation of Defect Characteristics and Carrier Transport Mechanisms in GaN Layers With Different Carbon Doping Concentration

“…Note the hysteresis of Run3 and Run4 tends to decrease when increasing the ramping time (not shown here). This time-related turn-on behavior might relate to bistability between the ON-state filamentary conduction [21] and SCLC. The complicated forward I -V behavior can be interpreted with the help of the DLTS measurements and I -V characteristics at different temperatures, which will be discussed in Sections III-C and III-D. Fig.…”

“…The electrons in the GaN:Si layer and the holes in the GaN:C layer then can easily overcome the barrier, and the device turns on steeply. In addition, despite the holes capture mechanism, we would like to notice that other trap-and fieldrelated mechanisms can be considered leading to the device turning on [21].…”