Variation of minority-carrier diffusion length with carrier concentration in GaAs liquid-phase epitaxial layers

Abstract

Minority‐carrier diffusion lengths in GaAs at 298 K were determined in Ge‐doped p‐type layers and Sn‐doped n‐type layers by short‐circuit photocurrent measurements. The layers were grown by liquid‐phase epitaxy and utilized a 1‐ to 2‐μ top layer of Al_0.5Ga_0.5As to eliminate surface recombination. Electron diffusion lengths L_n of 7–8 μ were obtained at concentrations less than 1×10¹⁸ holes/cm³ with a decrease to 0.8 μ at 1×10¹⁹ holes/cm³. Hole diffusion lengths L_p of 2–4μ were obtained at concentrations less than 1×10¹⁸ electrons/cm³ with a decrease to 0.3 μ at 6×10¹⁸ electrons/cm³. The relatively constant diffusion length in p‐ and n‐type layers below concentrations of 1×10¹⁸ cm⁻³ is determined by nonradiative recombination. At hole concentrations above 1×10¹⁸ cm⁻³, the radiative recombination contributes to the decrease in L_n. For the n‐type layers, the rapid decrease in L_p above concentrations of 1×10¹⁸ cm⁻³ results from an increase of nonradiative recombination at high donor concentrations.