AlGaAs/GaAs heterojunction phototransistor with a double delta-doped base grown by AP MOVPE

Simulations of AlGaAs/GaAs heterojunction phototransistors

“…We applied ring-shaped emitter and base contacts; the collector contact was placed on the bottom surface of the HPT structure. At first we assumed the epitaxial layer parameters from our work [8] (Table 1) for the bulk-doped base design. …”

“…This kind of HPT structure is not sufficiently described in the literature. Based on simulation results we modified the epitaxial phototransistor structure with a double delta-doped base, which was described in our works [8,9] and was not previously optimised. This modified structure is presented in Figure 8.…”

“…To solve these problems, different HPT constructions have been proposed: a heterojunction phototransistor with a punch-through base to reach high gain, high speed, and low noise simultaneously [3,4]; a punch-through phototransistor with avalanche enhancement [5,6]; or a guardring design around the active region [7]. In our earlier papers [8,9] the n-p-n AlGaAs/GaAs heterojunction phototransistor with a thin 50 nm-thick Zn-delta-doped GaAs base was described. The use of a delta-doped sheet located at heterojunction bipolar transistor interfaces suppressed the heterojunction potential spike, which resulted in higher emitter injection efficiency (current gain) and lower knee voltage.…”

“…The goal is to improve such device parameters as current gain, sensitivity, and response times. At the first step of the modelling we simulated the phototransistor structure presented in our work [8], but with a bulk-doped base. The optimised parameters of this structure were used in the next step of simulations focused on AlGaAs/GaAs HPT with a delta-doped base, working with optical base bias as a two-terminal device or as a three-terminal device with electrical and optical base bias.…”