低温热处理温度对SiC衬底上CuAlO_(2)薄膜特性的影响

Influence of Low Heat Treatment Temperature on the Characteristics of CuAlO_(2) Thin Films Prepared on SiC Substrate

为了解决双极型碳化硅(SiC)功率器件中由于p型SiC在室温下难以完全电离所导致的p+n发射结注入效率低的问题,提出将p型CuAlO_(2)与n型SiC形成的异质结作为发射结以提高该结的注入效率。本文利用溶胶凝胶(sol-gel)方法,在4H-SiC衬底上制备了CuAlO_(2)薄膜,研究了低温热处理温度对CuAlO_(2)薄膜晶体结构、表面形貌、光学特性的影响。结果表明:较高的热处理温度可以促进中间产物CuO的生成,进而在固相反应阶段促进CuAlO_(2)相的产生,最终制备的CuAlO_(2)薄膜主要以CuAlO_(2)相的(012)晶向择优取向。随着低温热处理温度的升高,薄膜的表面均匀致密,空位缺陷含量降低,结晶质量提高。当低温热处理温度为300℃时,CuAlO_(2)薄膜晶粒尺寸约为35 nm。此外,CuAlO_(2)薄膜在可见光范围内的透过率超过70%,且随着预处理温度升高,薄膜光学带隙略有增加。

In order to solve the problem of low injection efficiency of p+n emitter junction caused by incomplete ionization of p-type SiC in bipolar SiC power devices at room temperature,our group proposed to use the heterojunction formed by wide bandgap p-type CuAlO_(2)and n-type SiC as the emitter junction.In this work,CuAlO_(2)thin films were prepared on 4H-SiC(0001)by sol-gel method.The influence of low heat treatment temperature range on the crystal structure,surface morphology and optical properties of CuAlO_(2)thin films were studied.The results show that the formation of intermediate product CuO can be enhanced at higher heat treatment temperature,promoting the generation of CuAlO_(2)phase in the solid phase reaction stage.The prepared CuAlO_(2)thin films are mainly oriented with the(012)crystal orientation of CuAlO_(2)phase with high crystal quality.In addition,the higher heat treatment in low temperature range is beneficial to obtain high quality CuAlO_(2)thin films with uniform surface and lower concentration of Cu-vacancy defect.The surfaces of the films are uniform with an average crystal grain size of approximately 35 nm when the heat treatment temperature in low temperature range is 300℃.The CuAlO_(2)thin films are highly transparent,with optical transmission exceeding 70%across the whole visible range.Meanwhile,the optical band gaps of the CuAlO_(2)thin films increases slightly with the increase of heat treatment temperatures in low temperature range.