Two-dimensional electron gas analysis on pseudomorphic heterojunction field-effect transistor structures by photoluminescence

The photoluminescence (PL) of a high density two-dimensional electron gas (2DEG) in pseudomorphic AlGaAs/InGaAs/GaAs hetero-field-effect transistor structures is investigated. The PL is dominated by a strong band from the 2DEG in the InGaAs quantum well (QW). The band width increases linearly with applied gate voltage, which directly reflects the two-dimensional density of states (2DDOS) below the Fermi-level. Using the effective electron mass from cyclotron resonance experiments to evaluate the 2DDOS, we determine directly the 2DEG density n_s from the PL spectral width. The n_s values obtained are in excellent agreement with n_s values from Shubnikov-de Haas measurements. The QWs have In-contentrations between 14% and 27%, widths between 7nm and 17nm, and n_s up to 2.6×10¹²cm⁻². PL-mapping experiments on wafers show excellent lateral homogeneity of the material composition.