Modulation of the n-channel conductivity in liquid phase epitaxially grown p-n-p doped GaAs submicron structures

Abstract

p‐n‐p doped GaAs structures with active n‐doped layers with thicknesses of 250 nm>d_n>15 nm and doping concentrations of 3×10¹⁸ cm⁻³>n≥1×10¹⁷ cm⁻³, and 6×10¹⁷ cm⁻³>p>7×10¹⁵ cm⁻³, have been grown by liquid phase epitaxy. The modulation of the n‐channel conductivity σ_nn(U_np) by an external potential U_np between the p and n‐layers has been measured at 77 and 300 K. The characteristic curves σ_nn(U_np) are interpreted by the modulation of the two‐dimensional carrier concentration n⁽²⁾ (U_np) with U_np and by the variation of the mobility μ_n(d^ef_n) on the effective channel thickness d^ef_n(U_np) . The sensitivity of the p‐n‐p structure to small variations in design parameters is shown for the threshold voltage U^th_np . In p‐n‐p specimens with n∼1×10¹⁷ cm⁻³, p1⁶ cm⁻³ and d_n≂40 nm, an unexpected enhancement of the conductivity up to one order of magnitude between 300 and 77 K is observed. This is explained essentially by a hole freeze out due to the high acceptor level of the Ge dopant in the p layers and simultaneous release of electrons in the n channel.