Influences of δ -doping time and spacer thickness on the mobility and two-dimensional electron gas concentration in δ -doped GaAs/InGaAs/GaAs pseudomorphic heterostructures

Abstract

A series of GaAs/In0.25Ga0.75As/GaAs pseudomorphic high electron mobility transistors (HEMTs) was grown by low-pressure metalorganic chemical vapor deposition. The respective influences of δ-doping time and spacer thickness on the two-dimensional electron gas concentrations and the mobilities were studied. The maximum mobilities, μ=5600 and 22 000 cm2/V s at 300 and 77 K, respectively, appeared at a spacer thickness of 100 Å with a δ-doping time of 0.2 min. A δ-doped GaAs/In0.25Ga0.75As/GaAs pseudomorphic HEMT with the above parameters was fabricated. This device revealed high saturation current density of 350 mA/mm, transconductance of 95 mS/mm, and broad maximum transconductance region of 2.5 V with geometry of 2×100 μm2 at room temperature. In addition, very high breakdown voltage (26 V) and low leakage current (≤2 μA at −26 V) were achieved.