Improved performance of ultraviolet AlGaN/GaN npn HPTs by a thin lightly-doped n-AlGaN insertion layer
Shaoji Tang,
Lingxia Zhang,
Hualong Wu,
Changshan Liu,
Hao Jiang
Affiliations
Shaoji Tang
State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510275, China
Lingxia Zhang
State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510275, China
Hualong Wu
State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510275, China
Changshan Liu
State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510275, China
Hao Jiang
State Key Laboratory of Optoelectronic Materials and Technologies, School of Electronics and Information Technology, Sun Yat-Sen University, Guangzhou 510275, China
We reported the improved performance of ultraviolet two-terminal Al0.1GaN/GaN npn heterojunction phototransistors with a 10-nm-thick low-doped n-type Al0.1GaN insertion layer between emitter and base. Optical current gain at 2 V bias was increased from 6.6 × 103 to 9.8 × 104 by inserting the thin undoped layer. Spectral response measurements showed a high ultraviolet to visible (350 nm/400 nm) rejection ratio of 6.7 × 104 under 2 V bias, while that of the control sample without the insertion layer is 2.4 × 103. Simulation analysis reveals that the conduction band notch at the interface of the base-emitter (B-E) heterojunction is lowered by the insertion layer, leading to a weakened electric field and a narrowed space-charge region at the interface. This effect can reduce the recombination in the B-E heterojunction and contribute to the improved gain performance of the phototransistor.
