Paolo Batoni

Measurement of piezoelectric coefficient of gallium nitride using metal-insulator-semiconductor capacitors

Gallium nitride cantilevers with metal-insulator-semiconductor capacitors were fabricated and characterized as a function of strain to determine the effective piezoelectric constant. These cantilevers were tested at room temperature through a combination of cantilever bending experiments, strain gauge measurements, and finite element modeling. By measuring the shift in flatband voltage to applied strain the magnitude of the piezoelectric charge induced is determined. The effective piezoelectric constant e31′ was determined from these measurements to be −0.57±0.03C∕m2.

Photocurrent spectroscopy investigation of deep level defects in Mg-doped GaN and Mg-doped AlxGa1−xN(0.20<x<0.52)

Pulsed infrared photocurrent spectroscopy is used to investigate deep levels in highly resistive metal organic chemical vapor deposition-grown, magnesium-doped aluminum gallium nitride metal-semiconductor-metal test structures in the range of aluminum fraction from x=0.0 to x=0.52. Some background level of photocurrent is observed at all infrared pump wavelengths between 1.35 and 4.0 μm. The photocurrent decay time is a decreasing function of aluminum fraction. A peak photocurrent energy is observed for each aluminum fraction. With increasing aluminum fraction, the peak blueshifts and narrows.

Nanotexturing in Ultraviolet Light-Emitting Diodes for Enhanced Light Extraction

We discuss the use of nanotextured surfaces to increase the light extraction efficiency of ultraviolet light emitting diodes (UV-LEDs). Design approaches, fabrication processes and challenges, and initial experimental results are discussed.