GaN films

Carbon dioxide is absorbed in water from a 25 per cent mixture in nitrogen. How will its absorption rate compare with that from a mixture containing 35 per cent carbon dioxide, 40 per cent hydrogen and 25 per cent nitrogen It may be assumed that the gas-film resistance is controlling, that the partial pressure of carbon dioxide, at the gas-liquid interface is negligible and that the two-lilm theory is applicable, with the gan film thickness the same in the two cases. 

Preliminary studies on the dimeric complex [But(H)Ga(/i-NEt2)]2, prepared by the addition of four equivalents of B Li to the gallium chloride complex [Cl2Ga(/i-NEt2)]2, proved to be air stable and produced gallium-rich GaN films at deposition temperatures as low as 250 °C using CVD. However, it was necessary to add an external nitrogen source in order to obtain 1 1 GaN films.279... 

Et2Ga(N3)(MeNH-NH2)] LP-MOCVD Si(lll) substrate, epitaxial GaN films, low growth temperatures employed, low contamination 292... 

The 71Ga and 14N spectra of several of these films also showed partially-resolved shoulders shifted to higher frequency and having shorter T relaxation times that were attributed to Knight shifts in more heavily unintentionally doped regions of the film. These Knight shifts were observed in other GaN film samples [53] and will be discussed in more detail in Sects. 3.4.3 and 3.4.4, where MAS-NMR was used to improve the resolution in polycrystalline powders of h-GaN. Section 3.3.2 also shows 71Ga and 14N MAS-NMR spectra of GaN. 

Gallane stibine adducts, 240, 241-242 Gallium compounds, 294-296 see also Gallanes GaN GaSb GaN films, precursors for, 257-258 GaSb films, 298, 299, 303-306 Geometric parameters... 

Amano, H. Sawaki, N. Akasaki, I. Toyoda, Y. 1986. Metalorganic vapor phase epitaxial growth of a high quahty GaN film using AIN buffer layer. Appl. Phys. Lett. 48 353-355. 

This again shows the importance of the flow characteristics and the deposition conditions. The amide [Ga(NMe2)3]2 only gave GaN films in the presence of additional ammonia however, very high growth rates of 100-150 nm min were foimd at impressively low temperatures of 100-400 °C [114]. 

Fig. 20. (a) PL spectra from InGaN Eu QDs with different excitation wavelengths. The arrows indicate the 622 nm lines assigned to Eu ions inside InGaN QDs. (b) PLE spectra for Eu emissions at 620.0, 622.3, and 633.5 nm in InGaN Eu QDs. The horizontally dotted lines are PLE base lines. The vertically dotted lines show the band-gap energy of GaN film (3.505 eV). The insets show the PLE spectra of the 5D2 - 7Fo transition of Eu3+ for emissions at 622 and 633.5 nm. Both (a) and (b) were measured at 5 K (reprinted with permission from Andreev et al. (2005b)). 

Reinacher and co-workers have performed light induced electron spin resonance (LESR) measurements [13] on GaN films and resolved a line at g = 1.997 which may be related to the deep donors observed in ODMR and EDMR measurements and discussed in the following sections. 

FIGURE 2 The ODMR signal detected on the DAP band ( 3 eV) of an Mg-doped GaN film (microwave frequency = 24 GHz and T = 1.6 K). The effective mass donor (EM), deep donor (DD) and Mg-related acceptor (Mg) resonances are indicated. 

In high resistivity GaN films, Glaser and co-workers observed ODMR on a broad band peaked at 3 eV and observed a second deep donor state at g = 1.978 [29]. Because the g value is between the effective mass donor and that of the first deep donor, they argued that the energy level was shallower than the first deep donor. Koschnick and co-workers [30] have also resolved a donor resonance atg - 1.96 in undoped fihns and a possibly different donor (also at g 1.96) in Mg-doped fihns using high frequency (70 GHz) ODMR. The existence of multiple donor levels was first proposed by Gotz and co-workers [31] based on their electrical measurements and these results seem to confirm that idea. 

FIGURE 4 The optically detected Ga and71 Ga ENDOR on the EM donor line of a GaN film. The quadrupolar splitting of the 69Ga line is indicated. The microwave frequency was 24 GHz and the temperature was 1.6 K. The PL used in the measurements was dominated by the 2.2 eV band. 

TABLE 2 Results of Hall measurements and SIMS analysis on Si-doped AlxGai.xN and GaN films [17]. 

A7.6 HRTEM characterisation of planar defects in GaN films on sapphire... 

Most wurtzite GaN films have been grown on either 6H-SiC(0001) (see Datareview A7.8) or sapphire (A1203) substrates. The orientation of sapphire most frequently used is C-plane (0001) although there have been some structural characterisation studies made for growth on A-plane (1120) [1-4] and R-plane (0112) [1,2,5-7] substrates. Other defects found in the a-phase include inversion domain boundaries, prismatic faults, nanopipes, pits, voids and cracks. The limited structural information available on bulk single crystals of a-GaN shows that they contain a low density of line dislocations and stacking faults near inclusions [12] (see Datareview A7.5). 

The most common substrates for the growth of cubic P-GaN have been GaAs and 3C-SiC, discussed in Datareviews A7.7 and A7.8 respectively. There have been some structural studies of P-GaN films grown on Si (001) [8] and MgO [1]. The major defects in the cubic material are stacking faults along the 111 planes and perfect edge dislocations at the interface [1,8-11]. 

L.T. Romano, GaN film courtesy of Hewlett Packard Optoelectronics Division.]... 

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