Study On The Mechanism And Method Of P-type Doping In GaN

Based on excellent properties, GaN material have been studied extensively and systematically in the last decades. But there are still lots of problems to be studied, especially in the aspect of p-type doping in GaN. This paper is performed under this background.In this paper the problems of the available methods were analyzed, based on these analyses a new method was devised to enhance the p-type doping efficiency by utilizing the superlattice structure. We systematically studied the mechanism of superlattice doping, analyzed the relationships of superlattice period and Al content with the doping efficiency, optimized the parameters of doping process. On the basis of these studies, we acquired some new achievements and conclusions include:1．The valence minibands effect of the AlGaN/GaN superlattice is believed to be the mechanism of superlattice doping. The formation of the valence minibands can lower the activation energy of the acceptors in AlGaN, which can greatly enhance the ionization ratio of the acceptors.2．The formation of the valence minibands of the AlGaN/GaN superlattice is mainly due to the polar effect and the strain effect. The difference of the averaged hole concentration with and without polar effect and strain effect can be about one magnitude.3．The analyses on the roles of the polar effect and strain effect are verified by experiments. The superlattice period, Al content and chamber pressure are optimized by experiments. Higher chamber pressure, Al content and a length of period around 20nm are benefit to the doping efficiency.4．A sample whose hole concentration and resistivity are 4．36×10¹⁸ /cm³ and 0．31Ω·cm respectively is obtained. This result is better than the available results of bulk GaN doping. This result does prove the efficiency of superlattice structure in p-type doping and find its application in the LED and HBT devices.