Role of Interface Layers and Localized States in TiAl-Based Ohmic Contacts to p-Type 4H-SiC

Abstract

We have investigated the roles of interfacial reaction, work function variation, and localized states of annealed Ti/Al ohmic contacts to p-type 4H-SiC. The Al was found to be absent in the near interface region. The possibility of additional p-doping by Al indiffusion in the top SiC layer was ruled out. The work function of Ti 3 SiC 2 , the direct contact layer to SiC, was determined to be intermediate between Ti and p-SiC, leading to a considerably lowered Schottky barrier height. Reaction-induced interfacial states were observed in the near-interface SiC, which may further reduce the barrier height and cause the formation of ohmic contact.

Introducing Ohmic Contacts into Silicon Carbide Technology

“…That is, a large amount of Al diffuses into the SiC and introduces a heavily p-doped SiC, which result in narrower depletion area and thus more tunneling. As a matter of fact, this has also been suggested by analyzing interfacial chemical composition and local states, which shows that no additional Al segregates to interface, suggestive of a clean contact of Ti 3 SiC 2 to SiC (Gao et al, 2007). In support of this idea, we present in Fig.…”

Very low specific contact resistance measurements made on a highly p-type doped 4H-SiC layer selectively grown by vapor-liquid-solid transport

“…11,12 In contrast, extracted values of U b vary significantly even if our highest and lowest SBH can be compared to those reported in the literature. 17,18 As a consequence, the variation of the SCR is mainly related to a fluctuation of the SBH. Since the SBH is related to the intimate metal/4H-SiC interface, something is happening either during the VLS growth or contact annealing which favors or not the lowering of the SBH.…”

Step-flow growth of nanolaminate Ti3SiC2 epitaxial layers on 4H-SiC(0 0 0 1)

“…In such electronic device applications, a challenge is the formation of ohmic contacts to the SiC, as well as the durability of the contacts when operated at elevated temperatures. High-temperature annealed Ti/Al contacts on p-type SiC have been reported to form Ti 3 SiC 2 [5-8], which is suggested to contribute to the ohmic behavior of the contacts [9][10][11].Formation of Ti 3 SiC 2 and subsequent ohmic behavior has also been reported for hightemperature annealed Ti-based contacts on n-type SiC [12,13]. Here, we investigate the growth of Ti 3 SiC 2 thin films on 4° off-cut 4H-SiC using DC magnetron sputtering from three sources.…”

“…In such electronic device applications, a challenge is the formation of ohmic contacts to the SiC, as well as the durability of the contacts when operated at elevated temperatures. High-temperature annealed Ti/Al contacts on p-type SiC have been reported to form Ti 3 SiC 2 [5][6][7][8], which is suggested to contribute to the ohmic behavior of the contacts [9][10][11].…”