Progress on and challenges of p-type formation for GaN power devices
Progress on and challenges of p-type formation for GaN power devices
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DOI：
10.1063/5.0022198
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发表时间：
2020-09-07
影响因子：
3.2
通讯作者：
Tokuda, Yutaka
中科院分区：
文献类型：
--
作者：
Narita, Tetsuo;Yoshida, Hikaru;Tokuda, Yutaka
研究了垂直GaN功率器件的p型区制备工艺。沟槽栅金属氧化物半导体场效应晶体管的p型体层要求精确控制有效受体浓度，该浓度等于Mg受体浓度（N-a）与补偿供体浓度（N-d）之差。在生长过程中，碳原子通过金属有机气相外延取代氮位点（C-N），并在p型氮化镓层中作为供体源。由于间隙H原子（Hi）也可以补偿空穴，因此将它们从掺杂mg的层中移除是至关重要的。延长退火以释放氢原子，会形成额外的空穴陷阱。由于p(+)/p（-）结处的电场作用，p（+）封盖层可以有效和快速地从p型体层中去除H原子。另一方面，需要通过Mg离子注入选择性区域p型掺杂来控制器件边缘的电场分布。超高压退火（UHPA）在1GPa的氮气压力下，可以使植入后退火达到1753K而不发生热分解。阴极发光光谱和霍尔效应测量表明，在1673K以上退火时，受体活化比在1573K以下退火时显著提高。高温UHPA还能诱导Mg原子扩散。我们证明了空位扩散和来自UHPA环境的H原子的引入在Mg原子的再分布中起着关键作用。
The fabrication processes of p-type regions for vertical GaN power devices are investigated. A p-type body layer in a trench gate metal-oxide-semiconductor field-effect transistor requires precise control of the effective acceptor concentration, which is equal to the difference between the Mg acceptor concentration (N-a) and the compensating donor concentration (N-d). The carbon atoms incorporated during growth via metalorganic vapor phase epitaxy substitute nitrogen sites (C-N) and function as donor sources in a p-type GaN layer. Since interstitial H atoms(Hi ) also compensate holes, their removal from an Mg-doped layer is crucial. Extended anneals to release H atoms cause the formation of extra hole traps. The p(+) capping layer allows effective and rapid removal of H atoms from a p-type body layer owing to the electric field across the p(+)/p(-) junction. On the other hand, selective area p-type doping via Mg ion implantation is needed to control the electrical field distribution at the device edge. Ultrahigh-pressure annealing (UHPA) under a nitrogen pressure of 1GPa enables post-implantation annealing up to 1753K without thermal decomposition. Cathodoluminescence spectra and Hall-effect measurements suggest that the acceptor activation ratio improves dramatically by annealing above 1673K as compared to annealing at up to 1573K. High-temperature UHPA also induces Mg atom diffusion. We demonstrate that vacancy diffusion and the introduction of H atoms from the UHPA ambient play a key role in the redistribution of Mg atoms.