High optical anisotropy of the <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><mml:mrow><mml:mi>Ga</mml:mi><mml:mi>Sb</mml:mi></mml:mrow><mml:mo>/</mml:mo><mml:msub><mml:mi>Ga</mml:mi><mml:mi>x</mml:mi></m

We present the investigation of optical transitions in an <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><a:mrow><a:mi>Ga</a:mi><a:mi>Sb</a:mi></a:mrow><a:mo>/</a:mo><a:mrow><a:mi>Ga</a:mi><a:mi>In</a:mi><a:mi>As</a:mi><a:mi>Sb</a:mi></a:mrow></a:math>-based heterostructure through different experimental and numerical methods. The transitions had high-temperature stability, with them being observed in the 10–300 K temperature range. Four pronounced optical transitions are observed at low temperature with three of them being nonpolarized and one showing a degree of linear polarization higher than 60%. Time-resolved measurements of the transitions showed a complex carrier dynamics with several distinct processes related to the investigated interface. Using several numerical methods, we identified that the highly polarized transition originates from the first electron state in the <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><d:mrow><d:mi>Ga</d:mi><d:mi>In</d:mi><d:mi>As</d:mi><d:mi>Sb</d:mi></d:mrow></d:math> layer and a two-dimensional hole gas created within a triangular quantum well at the interface with the -type doped <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"><g:mrow><g:mi>Ga</g:mi><g:mi>Sb</g:mi></g:mrow></g:math> layer. The optical polarization of the signal originates in directional elongation of the atomic bonds enhanced by possible local composition fluctuations and the inheritance of these properties by the signal from the triangular quantum well. Such physical phenomena have the potential to be used as an internal polarizing filter in structures designed for midinfrared optoelectronics.