Predicted Mobility of 2-D Electrons in c-BN/Diamond Heterostructures

The cubic BN (c-BN)/diamond heterostructure proposed recently to possess 2-D electron gas (2DEG) could be a solution to diamond n-type field-effect transistors (FETs). However, the growth of c-BN/diamond system is still challenging. This work theoretically investigates the electronic transport property of c-BN/diamond heterostructure and explores its potential in electronic devices fields. The 2DEG sheet density in the heterointerface is calculated considering the effects of Schottky barrier height and modulation doping (MD) in c-BN barrier layer. The 2DEG mobility is the sum of five possible scattering mechanisms. The results show that the 2DEG mobility of c-BN/diamond heterostructure could be higher than 3000 cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text {V}\cdot \text { s}$ </tex-math></inline-formula> at room temperature for 2DEG sheet density of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\sim 10^{{12}}$ </tex-math></inline-formula> cm<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">−2</sup> with a Schottky barrier of 1.1 eV and the undoped c-BN barrier thickness of 20 nm. Acoustic phonon (AC) scattering is the main scattering mechanism of the 2DEG for relatively large range of the c-BN layer thickness at room temperature. Remote surface roughness (RSR) scattering could dominate with very thin c-BN layer (<6 nm) if dense 2DEG was available even without MD, or otherwise, the MD scattering could dominate for thin c-BN layer if 2DEG mainly originated from the doping ionization. The temperature-dependent 2DEG mobility is determined by the phonon scatterings for temperature higher than ~100 K.