Resistivity control in unintentionally doped GaN films grown by MOCVD

Deep traps in AlGaN/GaN heterostructures studied by deep level transient spectroscopy: Effect of carbon concentration in GaN buffer layers

“…All traps, both electron and holelike, exhibit a strong dependence on filling pulse width, indicating their association with extended defects. These results are consistent with an early study on the relationship of GaN resistivity to film microstructure and impurity compensation by Wickenden et al 7 It was concluded from that study that ͑i͒ with increasing growth pressure, the GaN films exhibit increasing grain size, decreasing density of threading edge dislocations, decreasing carbon and oxygen concentrations, and decreasing resistivity, and ͑ii͒ threading edge dislocations play a major role in the compensation mechanism of GaN, with carbon impurity segregation at or near the threading dislocations providing compensating acceptor states. In this study, we observe that with increasing growth pressure of GaN buffer layers, AlGaN/ GaN heterostructures exhibit a variety of electron traps in the GaN buffer layer, holelike traps near the AlGaN/GaN interface, decreasing dislocation-related electron traps, and decreasing carbon concentration.…”

“…Two wafers, one grown at 500 Torr and having a low ͓C͔ in the buffer layer and one grown at 100 Torr containing a high ͓C͔, were evaluated in this study. According to Wickenden et al, 7 carbon incorporation decreases from 4 ϫ 10 17 to 5 ϫ 10 16 cm −3 with an increase in growth pressure from 65 to 500 Torr. Each wafer was patterned with HFETs, Schottky barrier diodes ͑SBDs͒, and van der Pauw ͑VDP͒ structures and VDP and SBD samples were cut close to the center of each wafer for Hall-effect and DLTS measurements.…”

“…Carbon is a common residual impurity in unintentionally doped ͑UID͒ GaN buffer layers grown by metalorganic chemical vapor deposition ͑MOCVD͒ but the carbon concentration and resistivity in these layers can be controlled by growth pressure. 7 To increase the breakdown voltage and decrease drain leakage current of HFET devices, growth of GaN buffer layers with optimal resistivity and carbon concentration is necessary. In this work, we use temperature dependent current-voltage ͑I-V͒ and capacitance-voltage ͑C-V͒ measurements as well as DLTS measurements at different depths, different rate windows, and different filling pulse widths to investigate the effect of carbon concentration, ͓C͔, in the GaN buffer layer on deep traps in present in AlGaN/GaN devices.…”

MOCVD synthesis of group III-nitride heterostructure nanowires for solid-state lighting.

“…28 It has been suggested in numerous studies that carbon substituting on nitrogen sites, acts as a deep acceptor in GaN 22 , and increasing resistivity in GaN films with increasing carbon concentration has been previously reported. 29 Thus, increased incorporation of carbon from the trimethylgallium source at lower growth temperature 27 could lead to compensation of the free carriers in GaN. This explanation is also in agreement with the sharp decrease in the BEL/YL ratio for the 800 °C vs. 900 °C grown nanowires reported here.…”

Effect of H2O intentionally doping on photoelectric properties in MOVPE-growth GaN layers

“…In the previous study, the species of potential contaminants exist in gaseous sources and their effects on the properties of the epitaxial GaN layer had been discussed. Oxygen, carbon and hydrogen as main unintentional impurity elements were researched [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19] . These unintentionally elements in GaN layers could act as donor or acceptor dopants, which may effect the crystal quality, carrier density, carrier mobility and emission efficiency.…”