Research Of Different Thickness GaN Films And Study On Ohmic Contact To P-GaN

GaN-based Tritribe semiconductor materials have long been viewed as a promising system for the applications in anti radiation,high frequency,high power and high density integrated electronic devices and a variety of light-emitting,light detector,due to their wide direct bandgap,high saturated electron driftvelocity,small dielectric constant,good thermal performance and high temperature resistance,anti high electric field,acid alkali corrosion resistance and excellent chemical stability etc.For example,?-nitride-based light-emitting diodes(LEDS),because of their potential application to the next-generation solid-state lighting,have been rapidly developed.In this paper,the method is Epitaxial Lateral Overgrowth that we used to grow high-quality GaN crystal thin film on Sapphire Substrate by MOCVD.with someuseful ways of HRXRD,SEM,we characterize both the dislocation density and stress release in the GaN crystal thin film,and propose physical mechanism.Importantly,the influence of growing time on the crystal quality is investigate.On the other hand,Low-resistance ohmic contacts to p-type GaN developed by oxidizing Ni/Au thin films was reported,and,the processes of onmic contacts on p-GaN are optimized.The main results are as follows:1)The influence of the GaN exitaxial layer growth time on the crystal quality is meticulous researched.We measure X-ray rocking curve of the(002)plane and the(102)plane of GaN crystal thin films by HRXRD.The measurements show that the existence of in the edge dislocation density in the GaN film is two order of magnitude,compared with the screw discationdensity.It is found that with the increases of the GaN film thickness,the edge dislocation density has a significantly reduction,but the screw dislocation density change little.2)The specific contact resistance is characterized using a circular transmission line model(CTLM).With a optimization of the temperature and time in the procedure of rapid anneal,when the temperature,the time is 600 degrees Celsius and 60 second,a specific contact resistance below 9.0×10-4?.cm2 is obtained by oxidizing Ni(20nm)/Au(100nm)on p-type GaN in the atmosphere of O2.