Liquid phase epitaxial p-type ZnSe growth from a Se solution and fabrication of pn junctions with diffused n-type layers

Abstract

High concentration p-type epitaxial ZnSe layers are grown by the temperature difference method under controlled Zn vapor pressure (TDM-CVP) liquid phase epitaxy (LPE) from a Se solution. The hole concentration of the epitaxial layers grown at 950°C under a Zn vapor pressure of 3.0 atm increases with increasing the amount of Na 2Se until 0.5 × 10 −2 mol% in Se solution but decreases with an amount of Na 2Se above 0.5 × 10 −2 mol%. The decrease of the hole concentration is related to the appearance of a luminescence band with a peak at 2.696 eV in the CL spectra. These trends are in accordance with Na 2S- or LiN 3-doped epitaxial layers. Na 2Se-doped ZnSe layers show a high carrier concentration ( p max ≈ 1 × 10 18cm −3) and an almost undetectable deep level luminescence but an inhomogeneous surface morphology with many interrupted growth areas. On the other hand, Na 2S- or LiN 3-doped ZnSe layers show a relatively low carrier concentration (< 10 17cm −3) but an almost undetectable deep level luminescence and a homogeneous surface morphology with macrosteps. Photocapacitance measurements are applied to LiN 3-doped p-type epitaxial layers and revealed dominant deep levels at E v + 2.55 eV, which are suggested to compensate shallow acceptors. pn junction diodes are fabricated by Ga diffusion for n-type layers from a Zn solution into the Na 2S-doped p-type epitaxial ZnSe layer and they emit pure blue light with a wavelength of 471 nm at room temperature.