Influence of polarization charges in Al[sub 0.4]Ga[sub 0.6]N/GaN barrier varactors

Saglam, M.; Mutamba, K.; Megej, A.; Sydlo, C.; Hartnagel, H. L.; Daumiller, I.
January 2003
Applied Physics Letters;1/13/2003, Vol. 82 Issue 2, p227
Academic Journal
In this letter, we investigate the influence of polarization charges on the characteristics of metalorganic chemical-vapor-deposition-grown A1[sub 0.4]Ga[sub 0.6]N/GaN heterostructure barrier varactors (HBVs). The current-voltage and capacitance-voltage characteristics of the AlGaN/GaN HBVs shift asymmetrically due to the combination of piezoelectric (stress-induced) and spontaneous polarization effects in the barriers. Depending on the polarization of the bias voltage, different values of capacitance modulation, 1.4 for negative bias and 1.1 for positive bias, are observed. The obtained measurement results are supported by a theoretical analysis involving polarization charges at layer interfaces as well as their effect on the barrier height and the width of the depletion region.


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