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-In_(0.2)Ga_(0.8)N was grown on p-type layers by metal-organic chemical vapor deposition.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 inⅠ–Ⅴcurves 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 concentration.The influence of contact layer on the electrical characteristics of bulk p-type layers was then investigated by step etching technique using inductively coupled plasma etching and subsequent Hall-effect measurements.Identical values could be obtained consistently when a 28 nm non-conductive layer thickness at the surface was taken into account.Therefore,the procedures 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 conventionalⅢ–Ⅴmaterials.