Observation of a two-dimensional electron gas in low pressure metalorganic chemical vapor deposited GaN-AlxGa1−xN heterojunctions

We have confirmed the presence of a two-dimensional electron gas (2DEG) in a wide band-gap GaN-AlxGa1−xN heterojunction by observing steplike features in the quantum Hall effect. The 2DEG mobility for a GaN-Al0.13Ga0.87N heterojunction was measured to be 834 cm2/V s at room temperature. It monotonically increased and saturated at a value of 2626 cm2/V s at 77 K. The 2DEG mobility remained nearly constant for temperatures ranging from 77 to 4.2 K. Using Shubnikov–de Haas (SdH) measurements the two-dimensional carrier concentration was estimated to be 1×1011 cm−2. The peak mobility for the 2DEG was found to decrease with the heterojunction aluminum compositions in excess of 13%.