No abstract

No abstract

In this work, recessed gate AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) with double AlGaN barrier designs are fabricated and investigated. Two different recessed depths are designed, leading to a 5 nm and a 3 nm remaining bottom AlGaN barrier under the gate region, and two different Al% (15% and 20%) in the bottom AlGaN barriers are designed. First of all, a double hump trans-conductance (gm)–gate voltage (VG) characteristic is observed in a recessed gate AlGaN/GaN MIS-HEMT with a 5 nm remaining bottom Al0.2Ga0.8N barrier under the gate region. Secondly, a physical model is proposed to explain this double channel characteristic by means of a formation of a top channel below the gate dielectric under a positive VG. Finally, the impacts of Al% content (15% and 20%) in the bottom AlGaN barrier and 5 nm/3 nm remaining bottom AlGaN barriers under the gate region are studied in detail, indicating that lowering Al% content in the bottom can increase the threshold voltage (VTH) toward an enhancement-mode characteristic.

No abstract

Sputtered CdSe window layer can improve the short-circuit current density (J sc) of CdTe-based thin-film solar cell, however, meanwhile degrade the open-circuit voltage (V oc) and fill factor (FF). Herein, an oxygenation process is introduced during CdSe sputtering to improve this window layer's property for better device performance. The influence of oxygen on the CdSe is similar as the effect of oxygen on CdS. Incorporation of oxygen into the CdSe film promotes the formation of CdSeO 3 phase. Both V oc and FF of the CdTe solar cells are improved due to the formation of CdSeO 3 , and high efficiency (Eff.) of 18.6% is achieved. Efficiency improvement at module level is also demonstrated after applying the CdSe:O process in production line. This progress contributes to the CdTe-based thin-film module production for further efficiency improvement and cost reduction.