A comparison of the Hall-effect and secondary ion mass spectroscopy on the shallow oxygen donor in unintentionally doped GaN films

Abstract

We report on temperature-dependent Hall-effect measurements and secondary ion mass spectroscopy on unintentionally doped, n-type conducting GaN epitaxial films. Over a wide range of free carrier concentrations we find a good correlation between the Hall measurements and the atomic oxygen concentration. We observe an increase of the oxygen concentration close to the interface between the film and the sapphire substrate, which is typical for the growth technique used (synthesis from galliumtrichloride and ammonia). It produces a degenerate n-type layer of ≈1.5 μm thickness and results in a temperature-independent mobility and Hall concentration at low temperatures (<50 K). The gradient in free carrier concentration can also be seen in spatially resolved Raman and cathodoluminescence experiments. Based on the temperature dependence of the Hall-effect, Fourier transform infrared absorption experiments, and photoluminescence we come to the conclusion that oxygen produces a shallow donor level with a binding energy comparable to the shallow Si donor.

Investigation of Si and O Donor Impurities in Unintentionally Doped MBE-Grown GaN on SiC(0001) Substrate

“…This is unexpected, since previous reports suggest that O is the cause for the unintentional background doping. 31,32 High O concentration should therefore lead to high background concentration, whereas we observed the opposite.…”

Reduction of the dislocation density in HVPE-grown GaN epi-layers by an in situ SiNx treatment

“…Fig. 4b taken with the g [11][12][13][14][15][16][17][18][19][20] shows pure edge dislocations and mixed dislocations. From TEM images, a DD of $ 2.3 Â 10 9 cm À 2 is estimated at a thickness of $ 0.2 mm from the GaN/sapphire interface.…”

“…shows the cross-sectional weak-beam dark field TEM images recorded in the vicinity of GaN/sapphire interface. These micrographs were imaged with g 0002 and g [11][12][13][14][15][16][17][18][19][20] reflections to study screw (c-type), edge (a-type), and mixed (a + c type) dislocations. Fig.…”

Vapor-phase growth of high-quality GaN single crystals in crucible by carbothermal reduction and nitridation of Ga2O3

“…This intense luminescence peak indicates a good luminescence property of the crystals grown at these rates, compared with the relatively weak luminescence peak of the bar crystals grown by the previously reported CRN method [11]. The upward energy shift of the band-edgerelated luminescence peak ($3.47 eV) from the reported value ($3.42 eV) is probably attributed to the high concentration of oxygen [20,21], described below. On the other hand, the crystals grown at the rates of 2 and 15 mmol/min show the weak and broad luminescence peaks at $3.4 and $1.8 eV (Fig.…”