A new structure of a 4H-SiC bipolar transistor with ultra-high current gain is proposed and analysed by simulation. A p-type Schottky contact serving as the conventional emitter region is introduced. By proper choice of the metal work-function, the injection efficiency of the minority carrier (electron) is promoted and may be close to unity. Therefore high current gain is realised due to the high electron current density injected from the p-type Schottky contact. The simulation results show that the current gain varies with the metal work-function and could reach ∼1000, which is attractive for the base-drive circuit. Moreover, the new structure simplifies the etching process compared with the conventional bipolar junction transistor.Introduction: In past decades, bipolar junction transistors (BJTs) based on 4H-SiC have developed rapidly, owing to the superior properties of silicon carbide for high-power and high-temperature applications. As a current-driven switching and amplifying device, it is important to improve the current gain of BJTs for reducing the power losses in the drive circuit. Reducing the base thickness is a direct way, but the blocking characteristic will be significantly degraded [1]. To reduce the surface recombination between SiC and SiO 2 along the emitter-base sidewall, a suppressed surface recombination BJT structure [2] and a deep-level-reduction process [3] were proposed with special fabrication procedures. Also, the double-base structure [4] and a single base with a buried layer [5] which could accelerate the electron transport in the base region were verified by experiment and simulation.In the early years, a Schottky heterojunction bipolar transistor was proposed and demonstrated [6]. The current gain has a significant improvement, owing to the high injection efficiency of minority carriers in the Schottky heterojunction barrier emitter. It is worth noting that the high minority-to-majority carrier ratio has been demonstrated in the silicon tunnel transistor [7]. Furthermore, using this injection theory, silicon heterojunction emitter transistors with a current gain over 25 000 have been fabricated [8], and some new structures with a excellent performance have also been proposed [9,10]. In this Letter, we report a 4H-SiC work-function-dependent (WFD) bipolar transistor that replaces the conventional emitter region with the selected p-type Schottky contact. Using the theory of minority carrier injection in the Schottky contact, a large injection ratio of the minority-carrier (electron)-to-majority-carrier (hole) could be obtained due to the suppression of the majority carrier current by the large barrier height at the metal-SiC interface. Thus, the current gain is improved. Furthermore, the blocking characteristic could be maintained by the design of a floating-plate at the Schottky metal periphery.