Impact of MgO spacer layer on microwave performance of MgZnO/ZnO HEMT
Sumit Chaudhary, Pawan Kumar, Md Arif Khan, Amitesh Kumar, Shaibal Mukherjee
Abstract
Abstract This article analyzes the direct current and small-signal parameters of MgZnO/ZnO (MZO) HEMT for microwave application. Further, the impact of the MgO spacer layer on the microwave performance parameters such as transconductance ( g m ), cut-off frequency ( f T ), maximum oscillation frequency ( f max ) and Johnson’s figures of merit (J-FOM) of MZO HEMT has been analyzed. MZO HEMT with MgO spacer results in the enhanced values of two-dimensional electron gas (2DEG) density of 7.2 × 10 13 cm −2 and g m of 91 mS mm −1 . The values of f T and f max exhibit 3-fold enhancement to 5.57 GHz and to 7.8 GHz, respectively, and J-FOM is increased by 2.93 times with the introduction of MgO spacer layer in HEMT structure. Moreover, the impact of MgO spacer is studied on the off-state breakdown mechanism of MZO HEMT. The off-state breakdown voltage ( V br ) of MZO HEMT is ∼25 V higher than that for MZO HEMT with an MgO layer. Therefore, there is a trade-off between the microwave performance and the device off-state breakdown voltage. This work is significant for the development of large-area and cost-effective ZnO-based HEMTs for microwave applications.