Photoreflectance study of GaAsSb∕InP heterostructures

Abstract

Photoreflectance ͑PR͒ spectroscopy experiments are reported on GaAsSb/ InP heterostructures. The GaAsSb PR spectrum is studied as a function of temperature and the transition nature is shown to change from Franz-Keldysh oscillations ͑FKO͒ at room temperature to a third derivative functional form ͑TDFF͒ line shape at low temperatures. Combining both analysis ͑FKO and TDFF͒ in the same sample, we derive internal electric field and phase values of the PR transition, together with accurate values for alloy band gap energy on the whole temperature range. Type II interface recombination is shown to reduce photovoltage effects as a function of temperature. FKO are found to appear for a very weak electric field ͑8k V/c m ͒ in the GaAsSb/ InP heterostructure, contrary to usual observations. This point is discussed in relation with the broadening parameter of the transition.

Diodos emissores de luz como fonte de bombeio em fotorefetância.

“…Estes resultados demonstram a eficácia dos LEDs na modulação óptica de PR. Parece existir um consenso nos artigos científicos de que o sinal de PR vem da modulação do campo elétrico interno, existente em alguma interface ou na superfície (interface semicondutor/ar) da amostra DUttA, 1995), (CHOUAIB et al, 2005), por meio da injeção de pares elétron-buraco fotogerados. Sugere-se também que o mecanismo de modulação que dá origem ao sinal de PR em poços quânticos está relacionado com as variações periódicas induzidas pelo feixe de bombeio na população dos níveis do poço, o que afeta o perfil de potencial e, por sua vez, modifica os estados de energia (efeito Stark quântico confinado) (tANG, 1991).…”

Local micro-photoreflectance spectroscopy measurements on type II InGaAlAs/GaAsSb/InP heterojunction bipolar transistor: Correlation with electrical characteristics

“…PL and PR offer the advantage of being nondestructive and contactless methods, they can provide a number of valuable information and are able to measure some critical parameters for the HBT application, like in our case the InGaAlAs bandgap, the InGaAlAs/GaAsSb interface nature (type I or type II), and its band offset discontinuity, or in some other cases the surface Fermi level which provides a guide for predicting the contact resistivity. [11][12][13] In addition, room temperature PR spectroscopy has proven a significant ability in the qualification of HBT epitaxial structures. Similar studies have been widely published in the literature.…”

“…Note that the type II PL from GaAsSb/InP interface has already been observed and analyzed. 11,18 The PL measurements were carried out using an Ar laser as a light source. The samples are placed in a closed cycle He cryostat with a stable temperature of 10 K. The PL emission is dispersed through a Jobin-Yvon model HR-640 spectrometer and detected using nitrogen cooled InSb photodiode.…”

“…The significant blueshift of the PL peak with increasing excitation power is attributed to the band bending effect due to the spatial separation of electrons and holes at the InGaAlAs/GaAsSb interface, and this is a signature for a type II interface recombination. 11,18 The significant blueshift is understood as follows: Because electrons and holes are attracted to each other, narrow triangular shaped quantum wells (QW) are formed at the interface. When the optical power increases, carriers are accumulated in the QW increasing the confinement energy of the wells as well as the dipole energy across the interface.…”