A strategy for performance enhancement of HfInZnO thin film transistors using a double-active-layer structure

• Double channel to fabricate HfInZnO thin film transistor (TFT)
• Improvement in both mobility and negative bias stability of HfInZnO-TFTs
• Capacitance–voltage method to analyze the trap charges and the doping density
• Calculating the thickness of the induced channel layer

We investigate the electrical performance and negative bias stability of thin film transistors (TFTs) using double active layer. Double active layer is consisting of low oxygen content HfInZnO film as bottom channel and high oxygen content HfInZnO film as back channel. The HfInZnO-TFT with double channel layer shows a high mobility of 6.8 cm2/V s, a low threshold voltage of − 0.3 V, and a threshold voltage shifts of 0.65 V under − 20 V gate bias for 7200 s. The results suggest that HfInZnO with low oxygen content as the bottom channel could provide high carrier concentration and good HfInZnO/Al2O3 interface to improve field-effect mobility and negative bias stress stability. HfInZnO with high oxygen content as back channel can control the conductivity to reduce the off current of TFT. Thus, a double-active-layer structure is an effective way to improve the electrical performance of HfInZnO-TFT.