A high-gain, high-bandwidth In0.53Ga0.47As/InP heterojunction phototransistor for optical communications

Abstract

We describe investigations of the effects of inserting a thin, low-doped layer into the emitter of an InP/In0.53Ga0.47As heterojunction phototransistor (HPT). This high-low emitter structure has improved sensitivity and bandwidth over conventional structures at low input optical power by decreasing the bulk recombination current at the heterointerface. Experimental data show that the photocurrent gain is independent of the incident optical power at high input powers, corresponding to a heterojunction ideality factor of 1. At low input power, the gain is found to have a small power dependence, with an ideality factor of 1.25. A current gain as high as 260 is obtained at an input power of only 40 nW. These results, which are consistent with numerical simulations of the HPTs, give direct evidence that bulk recombination in the space- charge region at the emitter/base junction is the major source of recombination current for an InP/In0.53Ga0.47As HPT. A second structure is also proposed to improve the sensitivity by inserting a heavily doped layer into the base.

Influence of structural defects on carrier recombination and current gain in an InGaAs/AlGaAs/GaAs heterojunction phototransistor

“…[1][2][3][4] The optimum HPT design, in order to achieve high photosensitivity with low dark current, requires that the absorption of light in the emitter and the base regions be minimized, 4 thereby requiring the insertion of lower band gap absorption layers in the collector region. 5 Due largely to the transparent nature of GaAs substrate and the maturity of GaAs-based epitaxial growth techniques, the InGaAs/AlGaAs/GaAs-based system, in which InGaAs/GaAs layers form the absorption region in the collector and AlGaAs/GaAs acts as the emitter-base heterojunction, is a leading candidate for HPTs that can be vertically integrated into parallel optical systems.…”

Performance optimization of Pnp InGaAs/InP heterojunction phototransistors

“…6b, when the HPT does not have an intrinsic layer, the barrier at the E-B junction implies a more difficult injection of holes, whereas back injection of electrons is easier. Inserting an undoped InGaAs layer between base and emitter can avoid this situation [10,18]. What is more, under 0-0.3 V bias, the total current increases monotonously as the thickness of intrinsic layer increases.…”

“…The HPTs made of III-V compound semiconductors have been studied for two decades for its potentials as highperformance photodetectors [9,10], such as AlGaAs/GaAs and InGaAs/InP material systems. However, the HPTs also have some drawbacks that limit their applications in optoelectronic systems.…”

60 GHz sources using optically driven HBTs

“…The development of large bandwidth millimeter wave systems requiring a low-loss, lightweight, and interference free transmission medium has stimulated recent research in the area of optically controlled millimeter wave devices [1,2]. In addition, there has been considerable interest in the development of HBT phototransistors as an alternative to p-i-n detectors because HBTs can provide large photocurrent gains without high bias voltages and excess avalanche noise characteristics [3]. In the series of experiments presented here, high frequency heterojunction bipolar transistors are used as…”