Characterization of Substrate-Trap Effects in Hydrogen-Terminated Diamond Metal-Oxide-Semiconductor Field-Effect Transistors

Mechanisms of trap effects are crucial to improving diamond-based transistor electrical performance. Here, the trap effects in hydrogen-terminated diamond metal-oxide-semiconductor field-effect transistors (HD MOSFETs) are investigated by separating the effects of gate dielectric bulk alumina (BA) and diamond substrate (DS) for the first time. First, the location of traps and their impact on the dynamic drain current are characterized by pulsed {I} - {V} characterization. The dynamic drain current is degraded by traps in both BA and DS. Furthermore, the quiescent-bias-point-dependent trapping effects are studied by different quiescent bias points to reveal the response intensity of these two kinds of traps. Second, to further respectively characterize the effects of traps in the BA and the DS on HD MOSFETs, the threshold voltage ( {V}_{\text {th}} ) instability was characterized under negative gate bias stress (NGBS) conditions. Strong gate biases ranging from −4 to −8 V are selected to activate traps in DS. An extraordinary nonmonotonic change in {V}_{\text {th}} is found under the −8 V NGBS condition. Moreover, the corresponding variation in {V}_{\text {th}} is, unexpectedly, smaller than −4 and −6 V NGBS conditions. These phenomena indicate that the detrapping effect in the DS become dominant with increasing stress duration in the variation in {V}_{\text {th}} under an NGBS of −8 V. Finally, based on these results, an improved kinetic model is proposed to separately describe the effects of traps in the BA and the DS. These results are useful for improving the performance of HD MOSFETs.