Minority Carrier Transport and Their Lifetime in InGaAs/GaAsP Multiple Quantum Well Structures

Carlin, C. Zachary; Bradshaw, Geoffrey K.; Samberg, Joshua P.; Colter, P. C.; Bedair, S. M.

doi:10.1109/ted.2013.2268421

Cited by 8 publications

(1 citation statement)

References 15 publications

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“…In particular, thick barrier structures (~40 Å) can be used to investigate the recombination lifetime in InGaAs wells. This has been accomplished by comparing the modeled external quantum efficiency (EQE), including a modeled barrier tunneling lifetime, with measured device EQE [7]. For devices with thin barriers such that τ r ≫ τ tn the tunneling probability through the MQW structure is near unity and EQE matches that of GaAs control devices below the band edge (~870nm).…”

Section: Introductionmentioning

confidence: 99%

Determination of carrier recombination lifetime in InGaAs quantum wells from external quantum efficiency measurements

Bradshaw

Carlin

Samberg

et al. 2013

2013 IEEE 39th Photovoltaic Specialists Conference (PVSC)

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GaAs cells containing multiple quantum wells (MQW) of strained InGaAs/GaAsP can enhance efficiency in multijunction solar cells. Determination of carrier recombination lifetime in the InGaAs well is useful to understand material quality and carrier transport across the structure. GaAs p-i-n structures with and without strain balanced In 0.17 Ga 0.83 As wells and GaAs 0.25 P 0.75 barriers were grown by MOCVD on p-type GaAs substrates. The GaAsP barrier thickness was varied between devices to intentionally influence carrier transport. A decrease in EQE was observed as barrier width was increased, which was attributed to an increase in tunneling lifetime, τ tn . While this EQE decrease is undesirable in practical devices, it is useful for determining the recombination lifetime, τ r , of the InGaAs wells. The decrease in EQE was observed only at wavelengths of light greater than 600 nm, indicating that minority carrier electrons generated in the base are responsible for the reduction in EQE. Shorter wavelengths (<600 nm) of light are almost completely absorbed before reaching the base and primarily generate holes in the emitter. The tunneling lifetime and the currents generated in the p-i-n structures were modeled to calculate the EQE of a GaAs control and both thick and thin barrier MQW devices. The probability of transport through the entire MQW structure, P tot , was varied until the calculated EQE fit the experimental data. The value of P tot was then correlated to the only unknown parameter, the recombination lifetime. Using this method the recombination lifetime in In 0.17 Ga 0.83 As in the QW was determined to be 110 ns, which agrees with values found in previous time resolved photoluminescence measurements of metamorphic InGaAs films.Index Terms -quantum well solar cell, quantum efficiency, carrier recombination lifetime, InGaAs/GaAsP quantum well.

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Section: Introductionmentioning

confidence: 99%