Suitable contacting scheme for evaluating electrical properties of GaN-based p-type layers

A suitable contacting scheme for p-(Al)GaN facilitating quick feedback and accurate measurements is proposed in this study.22 nm p+-GaN followed by 2 nm p-In0.2Ga0.8N was grown on p-type layers by metal-organic chemical vapor depos-ition.Samples were then cut into squares after annealing and contact electrodes using In balls were put at the corners of the squares.Good linearity between all the electrodes was confirmed in I–V curves during Hall measurements even with In metal.Serval samples taken from the same wafer showed small standard deviation of～4%for resistivity,Hall mobility and hole concen-tration.The influence of contact layer on the electrical characteristics of bulk p-type layers was then investigated by step etch-ing technique using inductively coupled plasma etching and subsequent Hall-effect measurements.Identical values could be ob-tained consistently when a 28 nm non-conductive layer thickness at the surface was taken into account.Therefore,the proced-ures for evaluating the electrical properties of GaN-based p-type layers just using In balls proposed in this study are shown to be quick and useful as for the other conventional III–V materials.