Absorption Characteristics of ${\rm GaAs}_{1-x}{\rm Bi}_{x}/{\rm GaAs}$ Diodes in the Near-Infrared

Abstract

The absorption properties of a series of <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\rm GaAs}_{1-x}{\rm Bi}_{x}$</tex></formula> layers with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">${\sim}{6}\%$</tex></formula> Bi have been systematically investigated by measuring photocurrent spectra in p-i-n diode structures grown by molecular beam epitaxy. The <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">${\rm GaAs}_{1-x}{\rm Bi}_{x}$</tex></formula> layers varied in thickness from 50 to 350 nm and showed a photoresponse in the near-infrared up to almost 1.3 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$\mu{\rm m}$</tex></formula> . The absorption coefficients of the layers were obtained from the responsivity data. Below the band gap, the absorption coefficients showed an exponential dependence on the photon energy (Urbach tailing).