Low contact-resistance GaAs/AlGaAs regrowth interfaces and compositional grading layer formation during growth by metalorganic vapor phase epitaxy

Abstract

To obtain low contact resistance at the GaAs/AlGaAs regrowth interface in the selective growth of GaAs, growth conditions and pretreatment for cleaning the AlGaAs surface and forming a compositional grading layer have been investigated by employing reduced pressure MOVPE. When Si-doped GaAs is regrown on Si-doped AlGaAs at a substrate temperature of 700°C with an AsH 3/TMG molar flow ratio of 30, the density of depleted carriers created at the GaAs/AlGaAs regrowth interface reaches a value as high as 10 13 cm -2. The current-voltage relation of this heterostructure shows non-ohmic I– V characteristics. However, when Si-doped GaAs is regrown at a substrate temperature higher than 700°C with an AsH 3/TMG molar flow ratio smaller than 10, the carrier depletion region disappears in the carrier profile trace and contact resistance at the GaAs/AlGaAs regrowth interface is minimized to as low as 10 -5 to 10 -6 ω cm 2. From secondary ion mass spectroscopic analysis, it is found that a compositional grading layer is formed at the regrowth interface during growth. A model is proposed to explain compositional grading layer formation based upon Si neutral-pair diffusion.