KOH热湿腐蚀法准确估算GaN的位错密度

实验目的在于解决GaN外延层中六方形腐蚀坑起源问题存在的分歧,并利用腐蚀法准确地估计GaN的位错密度.大量对熔融KOH腐蚀GaN过程中表面形貌的演化以及温度和时间对腐蚀结果影响的实验结果表明,位错类型与腐蚀坑三维形状相对应,而与腐蚀坑大小无关,极性是GaN不同种类位错的腐蚀坑具有不同形状的决定性因素.使所有缺陷都显示出来所需的腐蚀温度和时间呈反比关系.腐蚀法估算GaN位错密度的准确性取决于优化的腐蚀条件和合理的微观观测方法.

Reliable evaluation of dislocation densities in GaN epilayers by molten KOH etching

The purpose of this paper is to deal with the controversy in the literature about the origins of the hexagonal-shaped etch pits in GaN epilayers formed by wet-chemical etching, and get a better estima-tion of dislocation densities. Intensive observations of GaN etching by molten KOH are focused on the morphology evolution during etching and the dependence of etching on time and temperature. It is the three-dimensional shape of etch pits that could be correlated with the dislocation type, instead of the size as many literatures presented, and polarity is found to be responsible for the formation of these different etch pit shapes. In addition, the needed etching time to reveal all the dislocations decreases with in-creasing needed temperature. A combination of the optimum etching condition and the proper microscopy measurement leads to a reliable evaluation of dislocation densities in GaN.