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

Abstract

P-type interface charge control layers for enabling GaN/SiC separate absorption and multiplication avalanche photodiodes Appl. Phys. Lett. 101, 093506 (2012) Recent improvements of the JET lithium beam diagnostic Rev. Sci. Instrum. 83, 10D533 (2012) Bulk and interfacial deep levels observed in In0.53Ga0.47As/GaAs0.5Sb0.5 multiple quantum well photodiodeWe have studied the influence of structural defects on the spatial variation of radiative and nonradiative recombination in an InGaAs/AlGaAs/GaAs resonant cavity enhanced npn heterojunction phototransistor ͑HPT͒ structure using cathodoluminescence ͑CL͒ and electron beam-induced current ͑EBIC͒ imaging. Absorber layers of InGaAs/GaAs multiple quantum wells ͑MQWs͒ are used to provide the photosensitivity for light with wavelengths that are transparent to the GaAs substrate. The current gain of the HPT under an applied bias voltage depends on the hole accumulation efficiency in the base and therefore on the hole lifetime. Strain relaxation-induced misfit dislocations in the MQWs are found to create regions of enhanced nonradiative recombination thereby reducing locally the hole accumulation efficiency and current gain. The reduction in the local EBIC signal caused by the dark line defects is less than ϳ20%, suggesting that misfit dislocations in this sample have a relatively small impact on overall device performance. EBIC and CL are found to be excellent complementary probes of the hole accumulation efficiency and relative recombination rates, owing to the high spatial resolution ͑ϳ1 m͒ of excitation of the electron beam used in these techniques. The temperature dependence of the EBIC and spectrally integrated CL images is examined for 85рTр300 K, and reveals that nonradiative recombination in the vicinity of misfit dislocations is predominantly thermally activated with observed spatial variations in lifetime and activation energy.

Cathodoluminescence study of band filling and carrier thermalization in GaAs/AlGaAs quantum boxes

“…At higher temperatures, other defect-related channels become active. Such nonradiative recombination is also thermally activated and can be enhanced by nearly two orders of magnitude as the temperature increases from 85 to 300 K. 8,9 A similar temperature dependence of the luminescence efficiency in nanostructures has been observed by Zhang et al, 10 who examined the photoluminescence of strain-confined GaAs/ AlGaAs quantum wires and QBs. It is thus evident that barriers which inhibit carrier collection can be found in a variety of nanostructure systems; the barrier height depends on the method and materials employed in the fabrication of the nanostructure.…”

Simulations of AlGaAs/GaAs heterojunction phototransistors

“…The software used for the phototransistor modelling is the Atlas device simulator from Silvaco 1 . This software simulates the electrical, optical, and thermal behaviour of different semiconductor devices (transistors, light emitters, detectors, solar cells).…”

“…Recently, they have been widely used in optoelectronic integrated circuits (OEIC) as optical switches or preamplifiers [1,2]. The HPT transistor can operate without a base bias ("floating base") because the optically generated carriers are responsible for its work.…”

Cathodoluminescence study of the influence of misfit dislocations on hole accumulation in an n-AlGaAs/p-GaAs/n-InGaAs heterojunction phototransistor

“…The current gain of an npn-type HPT depends strongly on the hole accumulation in the base. [2][3][4] Hole accumulation is a two step process that involves ͑i͒ escape of holes out of the quantum wells and transport to the base followed by ͑ii͒ recombination at the base-emitter junction. It is the aim of this letter to explore the influence of misfit dislocations on local variations in hole accumulation and demonstrate the degree to which defects can impact the HPT performance.…”

“…The AlGaAs/GaAs/InGaAs resonant cavity enhanced HPT structure studied here was grown by Epitaxial Products International who used low pressure metalorganic chemical vapor deposition. 3,4 The sample growth, on an n ϩ -GaAs substrate miscut 2°off ͑100͒, was initiated by an n ϩ -GaAs (3 ϫ10 18 cm Ϫ3 ) buffer layer, after which a high reflectivity n ϩ -AlAs/GaAs (3ϫ10 18 cm Ϫ3 ) quarter-wave stack was grown. Next, a 3940 Å n ϩ -GaAs subcollector (3 ϫ10 18 cm Ϫ3 ) and a 4410 Å InGaAs/GaAs MQW collector (5ϫ10 16 cm Ϫ3 ) were grown.…”