Ultrafast electron drift velocity overshoot in 3C–SiC E.W.S. Caetano a, * , E.F. Bezerra a , V.N. Freire a , J.A.P. da Costa b , E.F. da Silva Jr c a Departamento de Fı ´sica, Universidade Federal do Ceara ´, Caixa Postal 6030, Campus do Pici, 60455-760 Fortaleza, Ceara ´, Brazil b Departamento de Fı ´sica Te ´orica e Experimental, Universidade Federal do Rio Grande do Norte, Caixa Postal 1641, 59072-970 Natal, Rio Grande do Norte, Brazil c Departamento de Fı ´sica, Universidade Federal de Pernambuco, Cidade Universita ´ria, 50670-901 Recife, Pernambuco, Brazil Received 22 July 1999; accepted 22 July 1999 by D. Van Dyck; received in final form by the Publisher 15 November 1999 Abstract A theoretical study on the ultrafast high-field transport transient properties of electrons in 3C–SiC is performed within a parabolic and a nonparabolic band scheme. In both cases, the transient regime before the electron energy and drift velocity attain their steady-state is shown to be shorter than 0.2 ps. When the applied electric field intensity is higher than 300 kV/cm, an overshoot always occurs in the electron drift velocity, which is more pronounced when band nonparabolicity is considered.  2000 Elsevier Science Ltd. All rights reserved. Keywords: A. Semiconductors; D. Electronic transport Silicon carbide (SiC) carries a great potential for a new generation of advanced devices due to its physical (e.g. high stability, strong Si–C chemical bonding, large thermal conductivity, etc.) and electrical (e.g. high saturation velocity, large breakdown fields, low leakage current, etc.) properties. SiC may crystallize in either cubic or hexagonal forms, presenting a large number of polytypes. 3C–, 2H–, 4H– and 6H–SiC are some of the silicon carbide polytypes, each presenting characteristics that are particularly suitable for high-power, high-temperature, high-frequency, radiation- resistant, and light-emitting device applications. According to ab initio calculations [1–4], the SiC polytypes have a wide range of band gaps (1.27–2.10 eV) as well as carriers effective masses due to the remarkable differences in their band structures. The polytypes 3C–SiC E g  2:39 eV and 6H–SiC E g  2:86 eV have been extensively studied, in part because they present the highest saturation velocities under strong applied external electric fields, which suggests potential applications for submicron high-speed devices in the high-temperature domain. Although the best crystal quality nowadays has been attained with the 6H–SiC polytype, consideration of properties such as high mobility and high saturated drift velocity, associated with further developments on the growth processes, make 3C–SiC of great potential for developing high temperature and hazard safe electronic devices. 6H–SiC E g  2:86 eV is very promising for blue laser and light-emitting diode applications, but it has the lowest mobility of the polytypes, which is a drawback in several applications. In contrast, the high mobility and high saturation drift velocity of 3C–SiC makes it an important candidate not only for high-speed electronics, but also for high-temperature and high-power device developments up to the submicron level. The improvement of the SiC growth processes in the last years overcame several problems with sample preparation [5–8], and has a key role in those achievements. For reduced size devices, and in particular for high-speed/ high-field switching applications, nonstationary physical conditions are often imposed upon electron transport mechanisms, which lead to the electron drift velocity and energy time transients before steady-state transport con- ditions are attained. To date, investigations of the SiC high-field transport were restricted only to steady-state phenomena, principally the electron saturated drift velocity determination. Since the high-field electron transport transient should be important due to possible conduction Solid State Communications 113 (2000) 539–542 0038-1098/00/$ - see front matter  2000 Elsevier Science Ltd. All rights reserved. PII: S0038-1098(99)00522-0 PERGAMON www.elsevier.com/locate/ssc * Corresponding author. Fax: +55-85-2874138. E-mail address: valder@fisica.ufc.br (E.W.S. Caetano).