Abstract

Luminescence decay time has been measured in pure InGaAsP layers (Nd-Na- 10¹⁶ cm⁻³) whose composition corresponds to a band gap of 1.3μ⁽¹⁾. The sample was excited by a 1.06μ mode locked yag laser giving 100ps long pulses separated by 10ns. An accoustooptic cristal select one impulsion every 200ns to avoid heating of the sample and allow measurement of long decays. The carrier density is calculated by the knowledge of the excitation spot size and of the absorbed power. We make sure that the layer is situated at the beam waist by taking profit of the saturation of the absorption. The carriers density is varied between 4.10¹⁶ and 2.10¹⁹ cm⁻³ by changing the excitation intensity. The radiative recombination life time τ_r has been calculated with the Fermi golden rule, using the Kane model for the description of the lower conduction band and the three upper valence bands near the center of the Brillouin zone. The value of the matrix element is obtained by taking into account the measured absorption coefficient (α = 1.6 10⁴ cm⁻¹) at 1.06μ. The carriers life time τ is deduced from the luminescence decay time τ_L by taking into account the theoretical variation of the luminescence intensity as a function of the carriers density.

© 1984 Optical Society of America