Temperature and injection level dependencies and impact of thermal oxidation on carrier lifetimes in p-type and n-type 4H–SiC epilayers

Abstract

Dependencies of temperature and injection level on carrier lifetimes in 50 m thick p-type and n-type 4H-SiC epilayers have been investigated. The carrier lifetimes have been measured by differential microwave photoconductance decay measurements at various injection levels and temperatures. In both p-type and n-type epilayers, the carrier lifetimes gradually increased with increasing the injection level, which were naturally expected from the Shockley-Read-Hall ͑SRH͒ model, and after taking a maximum, the lifetimes dropped at the very high-injection level. In contrast, the carrier lifetimes exhibited continuous increase with elevating the temperature for both epilayers. In addition, the impact of thermal oxidation process on the carrier lifetimes has been also investigated. The thermal oxidation process, by which the Z 1/2 and EH 6/7 centers were remarkably reduced that had been observed in n-type 4H-SiC in our previous work, led to the improvement of the carrier lifetimes especially for n-type epilayers. The carrier lifetime reached 4.1 s in p-type and 6.1 s in n-type epilayers at 250°C with an injection level of 1.8ϫ 10 16 cm −3 through the thermal oxidation processing.

Temperature-Dependent Short-Circuit Capability of Silicon Carbide Power MOSFETs

“…According to [31]- [35], the temperature dependence of the saturation current I g_diff is given by the diffusion coefficient (D p and D n ), minority diffusion length (L p or L n ), and the intrinsic carrier concentration (n i ) as follows …”

Enhancement and control of carrier lifetimes in p-type 4H-SiC epilayers

“…Danno et al succeeded in achieving lifetime control for an n-type 4H-SiC epilayer by changing the Z 1/2 concentration using electron irradiation. 6 However, these beneficial results have mainly addressed the n-type 4H-SiC, with very few reports on the carrier lifetimes in thick and lightly doped p-type SiC, 14,15 which is often employed as the voltage-blocking region of high-voltage SiC switching devices such as thyristors 16 and insulated gate bipolar transistors (IGBTs). 17 In this work, the authors attempted to enhance carrier lifetimes in p-type 4H-SiC by employing thermal oxidation or carbon implantation, each of which is effective for lifetime enhancement in n-type SiC.…”

Impacts of reduction of deep levels and surface passivation on carrier lifetimes in p-type 4H-SiC epilayers

“…15 Therefore, the authors have investigated the factors affecting the carrier lifetimes in both p-type and n-type 4H-SiC epilayers, for example, the dependence of carrier lifetime on temperature and injection level. 16 As for the deep centers, the Z 1/2 center has been identified as the lifetime killer in n-type SiC, as mentioned above. On the other hand, the lifetime killer in p-type SiC has not yet been clarified.…”