High carbon doping of Al xGa 1− xAs (O ≤ x ≤ 1) by atomic layer epitaxy for device applications

Abstract

Atomic layer epitaxy (ALE) techniques are utilized in a conventional atmospheric pressure OMVPE reactor to achieve heavily carbon-doped Al x Ga 1− x As (O ≤ x ≤ 1) layers. Trimethylgallium, trimethylaluminum and arsine are the chemical precursors used i the reaction. Organometallic species present in the reaction environment are the sources of carbon. It is observed that both the carbon and hole concentrations in the grown layers are higher in nonsaturated ALE growth (growth rate 1 atomic layer per cycle) as compared to that of the layers prepared in saturated ALE growth (growth rate = 1 atomic layer per cycle). Also, the presence of trimethylaluminum during growths has enhanced the incorporation of electrically-active carbon. Hole carrier concentrations as high as 2 × 10 20 cm -3 have been achieved in Al 0.5Ga 0.5As layers. This is the highest electrically-active carbon doping level ever obta in growth by OMVPE. Device applications of this high carbon doping level to tunnel junction diode and nonalloyed contacts are demonstrated.