Characterization of piezoelectric and pyroelectric properties of MOVPE-grown strained (111)A InGaAs/GaAs QW structures by modulation spectroscopy

Abstract

The piezoelectric (PE) and pyroelectric properties of strained 〈111〉-oriented InGaAs layers have recently attracted interest because they provide additional device design parameters. However, there still exists a substantial uncertainty as to the value of the PE constant e14 as well as the value and sign of the pyroelectric coefficient. We applied both photoreflectance and contactless electroreflectance (CER) spectroscopy to assess the PE and pyroelectric properties of a strained InGaAs/GaAs quantum well (QW) structure grown on a (111)A GaAs substrate by metal organic vapor phase epitaxy. Photoreflectance and CER spectroscopy provide information on high-order QW transitions as well as the Franz-Keldysh oscillations that develop in the presence of electric fields in the GaAs barriers and lead to an accurate determination of the temperature dependence of the PE field and constant e14. High-resolution X-ray diffractometry and transmission electron microscopy were employed to independently determine the structural parameters and verify the high crystal quality of the QW structure. We observed a linear temperature dependence of the PE field and e14 in the range 25–300 K. To our knowledge, this is the first observation of the pyroelectric effect in strained InGaAs layers grown on (111)A GaAs substrates.