The GaAs-based metal-oxide-semiconductor heterostructure field effect transistors (MOSHFET) represent alternative devices to conventional Si MOS transistors. However, performance of GaAs MOSHFETs is still hindered by a high density of surface/interface states. We studied GaAs MOSHFETs prepared with aluminium oxide as a passivation and gate insulator layer. Heterostructures with an InGaAs channel, AlGaAs barrier, and GaAs contact layer were grown on semi-insulating GaAs substrate by metal-organic chemical vapour deposition. The surface of GaAs was covered in-situ by a thin Al layer, which was subsequently oxidized at room temperature to obtain aluminium oxide. Static and microwave characteristics and capacitance measurements showed good device performances. The GaAs-based MOSHFETs yielded higher sheet charge density and saturation drain current compared to the counterparts without an oxide surface layer. For MOSHFET devices with 1,5 μm gate length, the current gain and unilateral power gain cut-off frequencies of fT=19GHz and fmax=48GHz were extracted, respectively. Our results indicate an efficient suppression of the trap states on the GaAs surface.
Static transfer(left) and transconductance (right) caharacteristics of the GaAs-based MOSHFET and HFETs
Small-signal microwave performance of the GaAs-based MOSHFET measured at VDS = 3 V and VGS=−3.8 V.
Kordoš, P., Kúdela, R., Stoklas, R., Čičo, K., Mikulics, M., Gregušová, D., and Novák, J.: Aluminum oxide as passivation and gate insulator in GaAs-basedfield-effecttransistorsprepared in situ by metal-organic vapor deposition. Applied Phys. Lett. 100 (2012) 142113.
Kordoš, P., Fox, A., Kúdela, R., Mikulics, M., Stoklas, R., and Gregušová, D.: GaAs-based metal-oxide-semiconductorfield-effecttransistorwithaluminum oxide gate insulatorprepared in situ by MOCVD. Semicond. SciTechnol. 27 (2012) 115002.