Minority carrier diffusion lengths in liquid phase epitaxial InGaAsP and InGaAs

Abstract

Minority carrier diffusion lengths were determined for InGaAsP and InGaAs layers grown by liquid phase epitaxy on (100)-InP substrates by measuring the variation of the short circuit photocurrent as a focussed laser beam was scanned along a beveled (~1°) p-n junction. The effect of lattice-mismatch on the hole diffusion length (λ_p) for n-type unintentionally doped InGaAsP layers (λg=1.15 µm) was investigated for mismatch values from -0.25% to +0.31%, with the longest diffusion length (L_p = 1.5 µm) occurring when the epitaxial layer was lattice-matched to the substrate. As the amount of mismatch increased, L_p decreased. Electron diffusion lengths, L_n, were determined for lattice-matched quaternary and ternary layers grown from Zn doped melts over a wide range of hole concentrations. At the lowest hole concentrations, p = 3 × l0¹⁵ and 1.4 × 10¹⁶ cm⁻³, the electron diffusion lengths were 3.5 and 2.5 µm for the quaternary and ternary, respectively. As the hole concentration increased, L_n decreased and at the highest concentration (p = 5 × 10su18,cn⁻³) L_n was 0.13 µm for InGaAsP and 0.83 un for InGaAs.