Effective Electronic Structure of Monoclinic β−(AlxGa1−x)2O3\beta-(Al_xGa_{1-x})_2O_3 alloy semiconductor

In this article, the electronic band structure $\beta-(Al_xGa_{1-x})_2O_3$ alloy system is calculated with $\beta-Ga_2O_3$ as the bulk crystal. The technique of band unfolding is implemented to obtain the effective bandstructure \textit{(EBS)} for aluminium fractions varying between 12.5\% and 62.5\% with respect to the gallium atoms. A 160 atom supercell is used to model the disordered system that is generated using the technique of special quasirandom structures which mimics the site correlation of a truly random alloy and reduces the configurational space that arises due to the vast enumeration of alloy occupation sites. The impact of the disorder is then evaluated on the electron effective mass and bandgap which is calculated under the generalized gradient approximation \textit{(GGA)}. The EBS of disordered systems gives an insight into the effect of the loss of translational symmetry on the band topology which manifests as band broadening and can be used to evaluate disorder induced scattering rates and electron lifetimes. This technique of band unfolding can be further extended to alloy phonon dispersion and subsequently phonon lifetimes can also be evaluated from the band broadening

Beta-Ga2O3 MOSFETs with near 50 GHz fMAX and 5.4 MV/cm average breakdown field

This letter reports high-performance $\mathrm{\beta} Ga2O3 thin channel MOSFETs with T-gate and degenerately doped source/drain contacts regrown by MOCVD. Gate length scaling (LG= 160-200 nm) leads to a peak drain current (ID,MAX) of 285 mA/mm and peak trans-conductance (gm) of 52 mS/mm at 10 V drain bias with 23.5 Ohm mm on resistance (Ron). A low metal/n+ contact resistance of 0.078 Ohm mm was extracted from TLM measurement. Ron is dominated by interface resistance between channel and regrown layer. A gate-to-drain breakdown voltage of 192 V is measured for LGD = 355 nm resulting in average breakdown field (E_AVG) of 5.4 MV/cm. This E_AVG is the highest reported among all sub-micron gate length lateral FETs. RF measurements on 200 nm Silicon Nitride (Si3N4) passivated device shows a current gain cut off frequency (f_T) of 11 GHz and record power gain cut off frequency (f_MAX) of 48 GHz. The f_T.V_Br product is 2.11 THz.V for 192 V breakdown voltage. The switching figure of merit exceeds that of silicon and is comparable to mature wide-band gap devices