InGaN/GaN Visible-Light Heterojunction Phototransistor Featuring High Responsivity, High Speed, and Bias-Controlled Wavelength-Selectivity

Visible-light heterojunction phototransistors (HPTs) featuring high responsivity, high speed, and bias-controlled spectral response were fabricated using dopant-free polarization induced p-type base and InGaN(4 nm)/GaN(1.8 nm) superlattice (SL) absorber. Under 402-nm illumination of 0.16 mW/cm
²
, the fabricated HPTs exhibited a high photocurrent to dark current ( I
_ph
/ I
_dark
) ratio of 8 ×10
⁴
and a responsivity of 37 A/W at 1 V. The responsivity reaches 470 A/W at 3 V and the I
_ph
/ I
_dark
ratio is ~3.0. A high response speed with a rise time of ~3.4 ns was acquired. Moreover, due to the polarization effect in the SLs, the HPTs show bias-controlled wavelength selectivity without optical filter: narrowband response from 362 to 440 nm at bias ≤ 1.0 V, and broadband response below 440 nm at bias ≥1.5 V.