GaN substrates

A GaN substrate would be a help in this respect but it would need to be semi-insulating. In addition, GaN has a poor thermal conductivity and is not very suitable due to this negative material property. Aluminum nitride substrates may become the substrate of choice for GaN high-frequency applications. It has a reasonable thermal conductivity and is intrinsically semi-insulating but only time will tell. 

Trace element accelerator mass spectrometry (TEAMS) can also be applied for depth profiling as demonstrated for H, , , A1 and Si implants (and impurities) in semiconductor GaN substrate.115... 

II) slightly strained homoepitaxial layer of a small free electron concentration (about 1017 cm 3) on highly conductive GaN substrates ... 

B2.3 Epitaxy of III-N layers on GaN substrates B2.4 Alternative oxide substrates for GaN heteroepitaxy B2.5 Cubic substrates for growth of GaN and related compounds... 

The GaN substrates grown from nitrogen solution in pure gallium possess a high free-electron concentration of about 5 x 1019 cm 3 (if doped with magnesium, crystals are insulating [4]). This... 

B2.3 Epitaxy oflll-N layers on GaN substrates E (00.1) VERSUS (00.1) FACE... 

The main issue involving GaN substrates for nitride epitaxy concerns obtaining optoelectronic devices without mismatch dislocations. The critical conditions for misfit-dislocation creation include lattice mismatch between the layer and the substrate, layer thickness, growth conditions and substrate quality. 

So far, the following ternary layers grown on GaN substrates have been examined ... 

State-of-the-art, RMBE grown GaN/sapphire exhibits photoluminescence at 2 K which is dominated by a free A exciton (FEA), with visible transitions of excited FEAs and two excited FEBs, and linewidths are as narrow as 3 meV [47], Using GaN substrates for homoepitaxial RMBE growth, two donor bound excitons with an energy spacing of 0.9 meV have been resolved for the first time in low temperature photoluminescence (see FIGURE 3) [48], Additionally, the free C exciton becomes visible at about 80 K. 

Currently, the available single crystal GaN substrates are limited by the size and point defects that make them unsuitable for mass production [1]. An alternative to native GAN substrates is to use free-standing GaN templates prepared by hydride vapor phase epitaxy (HVPE), which has a typical thread dislocation (TD) density of 105-106 cm-2, however, the high price limits their availability [2],... 

The porous TiN has also been employed in the growth of GaN by HVPE. Researchers in Hitachi Cable Ltd use the porous TiN interlayer to facilitate the separation of free-standing GaN template from sapphire substrate [22]. This easy separation benefits from the existence of dense voids at the GaN/porous TiN interface. Recently, this company announced that it has prototyped a 3 in. GaN substrate based on this technology. 

Sapphire substrates, for II-Vl or III-V applications, can be found through the 100 mm range. Whereas, ZnSe, ZnTe, and GaN are found in the 1 cm range in research quantities. Efforts on ZnSe and related substrates increased with the demonstration of blue lasers in this material system. However, those efforts are foreshadowed by the blue LED and laser results in GaN. Presently there are several major research efforts underway to produce large area GaN substrates. The nitride substrate development effort also is motivated by high power, temperature and frequency device applications. For superconductors, lanthanum aluminate, strontium titanate, magnesium oxide, and other related substrates are found in the few to tens of square centimeter ranges. 

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