退火对非故意掺杂4H-SiC外延材料386nm和388nm发射峰的影响

Effect of annealing treatment on the 386 nm and 388 nm emission peaks in unintentionally doped 4H-SiC epilayer

10K条件下,采用光致发光(PL)技术研究了不同退火处理后非故意掺杂4H-SiC外延材料的低温PL特性.结果发现,在370—400nm范围内出现了三个发射峰,能量较高的峰约为3.26eV,与4H-SiC材料的室温禁带宽度相当.波长约为386nm和388nm的两个发射峰分别位于～3.21eV和～3.19eV,与材料中的N杂质有关.当退火时间为30min时,随退火温度的升高,386nm和388nm两个发射峰的PL强度先增加后减小,且退火温度为1573K时,两个发射峰的PL强度均达到最大.退火温度为1573K时,随着退火时间的延长,PL结果与30min退火的变化趋势一致.相同的退火条件下,386nm和388nm两个发射峰的低温PL结果与材料中本征缺陷的PL结果一致,是它们微扰势相互作用的结果.

Under different annealing treatment conditions,the low temperature PL properties of unintentionally doped 4H-SiC epilayer have been studied by photoluminescence （PL） technique at 10 K. The results show that there are three emission peaks in the range from 370 nm to 400 nm and the maximum energy is about 3. 26 eV,which is in accordance with the energy gaps （Eg） of 4H-SiC at room temperature. The 386 nm and 388 nm peaks （ corresponding to ～ 3. 21 eV and ～ 3. 19 eV,respectively） are related with N impurity. When keeping annealing time at 30 min,the PL intensity of 386 nm and 388 nm peaks increases and then decreases with the annealing temperature increasing and reaches a maximum at 1573 K. The PL at 386 nm and 388nm change in quite the same manner with annealing time during isothermal annealing at temperature of 1573 K,whereas the difference is small. With the same annealing treatment,the low temperature PL results of 386 nm and 388 nm coincide with that of intrinsic defects in unintentionally doped 4H-SiC,which results from the interaction of infinitesimal disturbance potential energy between N impurity and native defects.