Figures

Figure 1

Results of our theoretical calculation for the energy levels of a Coulombic donor state in GaN as a function of magnetic field (lines). Notation is that of isotropic H atom in low field limit. States are listed in order of increasing energy within each group in the legend (e.g., ns, 2p, 3p, 3d states). Points show corresponding perturbation theory (PT) results (only 3p- shown of n=3 states for clarity; others deviate similarly from accurate calculation).

Figure 2

Excitonic 1.7 K PL spectra of the undoped Epitronics HVPE-1 300 µm GaN/Al2O3 sample as a function of magnetic field in Faraday configuration with B||[0 0 0 1]. Only one of the two possible circular polarizations is detected in these spectra.

Figure 3

Excitonic PL spectra of the Epitronics HVPE-1 sample as a function of temperature.

Figure 4

Excitonic 1.7 K PL spectra of four Epitronics HVPE samples with various Si doping levels. Lowest spectrum is for undoped sample; next lowest is for sample with ND-NA = 5 x 1016 cm-3; second from top is for sample with ND-NA = 2.5 x 1017 cm-3; top spectrum is for sample with ND-NA = 4 x 1017 cm-3.

Figure 5

Shifted Raman spectrum (upper) and PL spectrum (lower) of the Lincoln Laboratories HVPE-2 sample; actual laser energy during the Raman measurement was 3.407 eV. The ERS peaks are denoted in the upper spectrum.

Figure 6

Electronic Raman spectra [ ] as a function of magnetic field at 1.7 K for the sample of Figure 5.

Figure 7

Reflectance spectrum of Epitronics HVPE-1 sample (top), and PL spectra of HVPE-1, the Lincoln Labs HVPE-2 sample, and an MOCVD sample (bottom three, listed from top to bottom).

Figure 8

1.7 K reflectance spectrum of Epitronics HVPE-1 sample recorded from the edge of the sample (see inset) in two orthogonal linear polarizations (upper spectrum, -polarization; lower spectrum, -polarization).

Figure 9

Room temperature reflectance (upper) and PL (lower) spectra of a 10 µm thick undoped HVPE Epitronics GaN/Al2O3 sample.

Figure 10

Long term stability of 300 K PL intensity of sulfide-treated HVPE GaN; intensity was 1.0 prior to treatment. Times refer to periods of continuous laser illumination.

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