Silicon carbide and silicon carbide:germanium heterostructure bipolar transistors

Abstract

In this letter, we report on heterostructure bipolar transistors ͑HBTs͒ based on silicon carbide ͑SiC͒ and a silicon carbide:germanium ͑SiC:Ge͒ alloy. The SiC:Ge base alloy was formed by the ion implantation of Ge into p-type 4H-SiC and subsequent annealing. HBT mesa structures were fabricated using a reactive ion etching process. The incorporation of Ge was found to increase the gain and the Early voltage of the devices. A common-emitter current gain ͑␤͒ of greater than 3 was measured for the SiC:Ge HBTs. Homojunction SiC transistors were fabricated as a reference using the same process ͑except no Ge in the base region͒ and exhibited a ␤ of 2.2. The transistors exhibited high breakdown voltages ͑Ͼ50 V without passivation͒, that typify SiC-based devices. These results indicate that SiC:Ge is a promising material for use in SiC-based heterostructure devices.

Theoretical Derivations of a Direct Band Gap Semiconductor of SiC Doped with Ge

“…SiC doped with a few percent of Ge by ion implantation technique showed a reduction of the forward voltage drop and built-in voltage. 4 Heterostructure bipolar transistors (HBTs) produced with Ge-incorporated SiC showed an increase in gain with common-emitter current gain (b) of greater than 3 compared to homojunction SiC transistors with b of 2.2; and increase in early voltage and high breakdown voltages were also exhibited by the SiC-Ge devices. 4 A US patent 5 described a Ge-SiC layer as a floating gate material in Electrically Erasable Programmable Read-Only Memory (EEPROM) and flash memory devices which resulted in increased tunneling currents and faster erase operations.…”

Defect investigations of SiCGe epilayer grown on 6H‐SiC

“…Only SiCGe alloy formed by ion implantation of Ge into a p-type 4H-SiC has been reported. [5,6] However, they did not investigate the microstructural properties of the SiCGe films on SiC. Moreover, SiCGe thin films grown by LPCVD have a higher Ge content and a variable C/Si ratio, which are different from the SiCGe films formed by ion implantations.…”

3C‐SiC:Ge alloys grown on Si (111) substrates by SSMBE

“…Therefore nonequilibrium methods of material synthesis must be chosen to form the required composition. Such methods are (1) ion beam synthesis [3,8,9], (2) plasma assisted deposition and (3) MBE at low temperatures [10]. In the present study our effort was to obtain Ge incorporation into the 3C-SiC lattice by using solid source molecular beam epitaxial (SSMBE) growth on Si substrates in order to create a cubic SiC:Ge alloy.…”