IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Thin Films Monday Sessions
       Session TF-MoP

Paper TF-MoP20
In-situ Buried Multiquantum Well Structures Studied by Photoreflectance and Photoluminescence Spectroscopy

Monday, October 29, 2001, 5:30 pm, Room 134/135

Session: Multilayers and Thin Film Characterization Poster Session
Presenter: A. Perez-Centeno, CINVESTAV-IPN, Mexico
Authors: A. Perez-Centeno, CINVESTAV-IPN, Mexico
M. Lopez-Lopez, CINVESTAV-IPN, Mexico
M. Melendez-Lira, CINVESTAV-IPN, Mexico
M. Tamura, CINVESTAV-IPN, Mexico
T. Ishikawa, OTL, Tsukuba, Japan
Correspondent: Click to Email
In this work we present the optical and structural characteristics of AlGaAs/GaAs multiquantum wells (MQWs) that were in-situ etched into mesa-stripe structures and then buried avoiding air-exposure of the active region at the sidewalls. The samples were fabricated using the following steps: First, by conventional photolithography and etching techniques mesa stripe-arrays of different widths and along different crystallographic directions were patterned on the surface of a 250nm thick GaAs protective layer of MQWs grown on a GaAs(001) wafer. The mesas depth was 200nm, in order to protect the MQWs a 50nm-thick GaAs layer was left unetched. Next the wafer was introduced into an UHV multichamber system with an MBE chamber and an etching chamber connected through UHV tunnels. The initial pattern was transferred down to the MQWs by in-situ Cl@sub 2@-etching to a depth of ~200nm. Then, the sample was transferred in UHV to the MBE chamber, where an AlGaAs layer was overgrown thus completing the in-situ buried structures. Photoluminescence (PL) studies showed a decrease in the MQWs PL intensity and PL lifetime for mesa stripes of several microns in width, thus showing the effects of carrier trapping and non-radiative recombination at the etched-regrown interfaces on the sidewalls. The PL degradation was stronger for mesas along the [110] direction. In the photoreflectance (PR) spectra the transitions associated to the MQWs were clearly observed for mesas along [1-1 0], however for mesas along [110] we only observed the signal associated to the GaAs band-gap. PR spectra also showed the presence of oscillations above the GaAs band-gap value associated to built-in internal electric fields. The strength of the internal electric fields was in the order of 10 kV/cm, as obtained by the Franz-Keldysh model. We discuss the degraded optical properties for mesas along [110] in terms of the increased difficulties to smoothly overgrow mesa-sidewalls along this direction.