Study on GaN and Pelated Compound Crystal Growth By ECR-MBE for Blue Lase

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Fundamental studies on GaN and related compound crystal growth were carried out by using electron-cyclotron-resonance molecular-beam-epitaxy (ECR-MBE) for semiconductor laser diode emitting in blue to ultra-violet light. ECR-MBE,which can effectively utilize excited species including atomic and molecular radicals and ions even in ultra high vacuum atmosphere, has several advantages over conventional epitaxial growth methods, which include 1)low temperature growth 2)on need for hydrogen gas 3)capability forin-situ observation by optical emission spectroscopy and 4)precise thickness control in atomic scale.Several useful experimental results are obtained from these studies. These include1)From optical emission spectroscopy, dominant excited species for GaN MBE growht were found to be atomic nitrogen. It was further found that hydrogen and helium gas addition to nitrogen gas is effective in obtaining excited species and as aresults in increasing growth rate. 2)Cubic and hexagonal crystal structure control was successfully realized by both III to V ratio and electric bias voltage. Both mechanism can be equally explained by effective III to V ratio control on the growing surface during growth. 3)LigaO_2 was found to be a suitable substrate for GaN MBE growth with is small lattice mismatch of around 1% to GaN.4)Growth mechanism explaining ECR-MBE growth should include desorption process induced by impinging ionic species.