Influence of indium segregation on the light emission of piezoelectric InGaAs/GaAs quantum wells grown by molecular beam epitaxy
C.M. Yee-Rendón, M. López-López, and M. Meléndez-Lira
Departamento de Física, Centro de Investigación y de Estudios Avanzados del IPN, Apartado Postal 14-740, 07000 México, D. F., Méx.
Recibido el 17 de septiembre de 2003. ]]> Aceptado el 11 de noviembre de 2003.
Abstract
Pseudomorphic In0.2 Ga0.8 As/GaAs quantum wells (QWs) were grown by molecular beam epitaxy (MBE) on GaAs substrates oriented along the (11n) direction, with n=1,2,3,4. The optical and structural properties of the heterostructures were studied by photoluminescence spectroscopy (PL) at 14, 77 and 300 K, and atomic force microscopy (AFM) measurements. The emission wavelength from the QWs has two contributions, a blue shift due to the compressive strain, and a red shift due to the quantum confined Stark effect produced by the piezoelectric field present in these materials. A traditional theoretical interpretation of the QWs emission employing a simple well model shows discrepancies with the experimental results. In order to satisfactorily explain the emission wavelength we proposed to include segregation effects of In at the wells interfaces. The matrix transfer method was implemented to solve numerically the Schrödinger equation taking into account In segregation effects by including an asymmetric potential well with a profile depending on the details of the In incorporation. With segregation effects included in the emission calculations, the theoretical predictions reproduce very well the experimental values of PL emission. Our results demostrate that in order to have efficient InGaAs QWs-based optoelectronic devices is very important to take into account interfacial segregation effects.
Keywords: Quantum wells; piezoelectric field; Indium segregation.
Resumen
Se crecieron pozos cuánticos pseudomórficos de InGaAs/GaAs por epitaxia de haces moleculares sobre sustratos de GaAs orientados en la dirección (11n), n=1,2,3,4. Se estudiaron las propiedades ópticas y estructurales por medio de fotoluminiscencia (FL) a 14, 77 y 300 K, y microscopia de fuerza atómica (MFA). La emisión de los pozos cuánticos tiene dos contribuciones, un corrimiento hacia el color azul debido al esfuerzo compresivo al que esta sujeto la heteroestructura y un corrimiento hacia el rojo debido al efecto Stark cuántico producido por el campo piezoeléctrico presente en estos materiales. Para explicar satisfactoriamente la energía de emisión de los pozos cuánticos proponemos incluir efectos de segregación de In en la interfaz de los pozos cuánticos. Implementamos el método de la matriz de transferencia para resolver numéricamente la ecuación de Schrödinger incluyendo los efectos de la segregación en el potencial de los pozos. Con la inclusión de los efectos de segregación en los cálculos de la emisión, las predicciones teóricas reproducen muy bien los resultados de FL.
Descriptores: Pozos cuánticos; campo piezoeléctrico; segregación de Indio.
]]> PACS: 68.65.Fg; 78.67; 81.07.St
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