Study Of The Growth Characteristics Of P-SiCGe Layers Grown On 6H-SiC Substrates

A lattice matched SiCGe epi-layer on SiC substrate can make greatly applications in visible or near infrared light in optoelectronics by changing its band gap via change composition ratio and make SiC-based devices to meet the needs in optoelectronic applications. This dissertation aims at the growth feature,process parameters and defects of p-SiCGe films on n-SiC substrate.The electrical characteristics of SiCGe/SiC pn heterojunction are also discussed.The main results in the work are as follows:1.SiCGe films were successfully grown in layer by layer mode.Firstly,growth features of the large flow rate and that of the low flow rate was compared.Secondly,the influence of the different Si/C ratio on SiC growth was studied,and 2D growth SiC layers were realized.Lastly, the influences of growth temperature and GeH₄ flow rate on SiCGe growth were studied.As the growth temperature increases,SiCGe layer growth changes from islands growth mode to layer by layer mode,and the content of Ge decreases.At 1250℃,the SiCGe samples have better surface morphologies,and Ge content of in them can be partly improved by increasing the GeH₄ flow rates.2.The principle of APB(Antiphase Boundaries)defects and DPB(Double Positioning Boundary)defects was analyzed.APB defects formed at the junctions of different growing sides of the steps on the substrate.DPB defects were caused by a different stacking order of 3C-SiC structure(ABC and ACB)which appeared in the SiCGe layer epitaxied on a 6H (ABCACB)substrate.3.p type SiCGe films were successfully grown.For the SiCGe samples grown with a B₂H₆ flow rate in a range of 0.2 to 1 sccm,they were identify as p type by the hot probe method and Hall effect measurement,and their doping concentrations were about 10²⁰cm^-3.4.The electrical characteristics of SiCGe/SiC pn heterojunction were tested and analyzed. The pn heterojunction has a rectificative current voltage characteristic,and its cut-in voltage is 1.6V when the current density is 0.03451A/cm².The current density is only 0.02697A/cm² at a reverse voltage of 10V,and it just increased to 0.07792A/cm² when reverse voltage is 20V.