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

利用电子回旋共振分子束外延（ECR-MBE）技术，对GaN及其相关化合物晶体生长进行了基础研究，并用于蓝、紫外半导体激光器的研制。ECR分子束外延（ECR-MBE）是一种在超高真空环境下也能有效利用原子分子自由基和离子等激发态的外延技术，与传统外延技术相比，具有生长温度低、不需要氢气、发射光谱原位观测和原子尺度厚度精确控制等优点。这些结果包括：1）从发射光谱中发现GaN分子束外延生长的主要激发态是氮原子。进一步发现，向氮气中添加氢气和氦气在获得激发物种方面是有效的，并且导致增加生长速率。2)通过III/V比和偏压控制，成功地实现了立方和六方晶体结构的控制。这两种机制可以同样地解释为在生长过程中生长表面上的有效III与V的比率控制。3）LigaO_2与GaN的晶格失配度在1%左右，是一种适合GaN MBE生长的衬底。4）ECR MBE生长的生长机理应该包括离子碰撞引起的脱附过程。

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.