Enhancement of hydrogen terminated diamond FET performance through integration of electron acceptor oxides

This work reports on the improvement to the performance of hydrogen terminated diamond field effect transistors (FETs) by replacing surface adsorbed atmospheric species with transition metal oxides MoO3 and V2O5, and the implementation of a pre-deposition vacuum anneal at 400°C which is required to maintain the stability of the doping within the devices. MESFET structures incorporating a metal/H-diamond gate contact were observed to be irreversibly damaged by exposure to the 400°C pre deposition vacuum annealing prior to deposition of MoO3 or V2O5. Therefore preliminary investigation of devices including the MoO3 or V2O5 without pre annealing was carried out. An increase in maximum drain current of up to 50% was observed when comparing output characteristics before and after deposition of MoO3 or V2O5 without the 400°C pre anneal. Following this, investigation of the inclusion of Al2O3 into the FET structure as a gate dielectric was explored in order to increase the thermal robustness of the gate and allow inclusion of the pre deposition vacuum annealing at 400°C. It was shown that FETs fabricated using Al2O3 as a gate dielectric maintained transistor operation after vacuum annealing at 400°C and deposition of 10nm of MoO3 or V2O5. FETs were characterized after exposure to atmospheric adsorbates, and after deposition of 10nm of MoO3 or V2O5 and pre deposition 400°C vacuum anneal. FETs with Al2O3 gate dielectric using V2O5 and pre deposition annealing showed an increase in drain current of up to 276%. The V2O5 FETs using Al2O3 as a gate dielectric showed maximum drain currents of -376mA/mm, extrinsic transconductances of 97mS/mm, and on resistances as low as 17Ω.mm. These are important parameters for assessing the performance of power FETs