High Pressure Solution Growth of GaN and Related Compounds

FIGURE 1 shows the equilibrium pN2 - T curves for AIN, GaN and InN. The curve for AIN was calculated by Slack and McNelly [6], The one for GaN was determined by Karpinski and Porowski [5] based on gas pressure and Bridgman anvil experiments performed by Karpinski et al [4], The curve for InN was obtained by Grzegory et al [7] and follows from differential thermal analysis (DTA) and annealing of InN at high N2 pressure. The curves for GaN and InN deviate from linear dependence at 

The melting temperatures of the nitrides (TABLE 1) are significantly higher than the maximum temperature available for each of the compounds in the gas pressure chamber. This causes a very low solubility of AIN, GaN and InN in the corresponding liquid metals. 

The solubility of N in liquid Ga was experimentally determined [7,8] for the conditions corresponding to the equilibrium pN2 - T curve. In the high pressure experimental system (20 kbar, 2000 K), the nitrogen content in Ga can be increased up to -1 at.% which is sufficient for effective crystallisation from the solution. 

Calculations [7,8] performed for AIN and InN suggest that the maximum nitrogen content in the solution for the A1-A1N system, determined by the technical limit for temperature (2000 K), is a few times lower than for GaN. 

For the In-InN system, the maximum concentration is determined by the available N2 pressure (20 kbar) which limits the stability range of the nitride to T 900 K. At such low temperatures, the expected concentration of N in liquid In is lower than 0.001 at.%. 

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B1.1 High pressure solution growth of GaN and related compounds... 

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