Using both faces of polar semiconductor wafers for functional devices.

Unlike non-polar semiconductors such as silicon, the broken inversion symmetry of the wide-bandgap semiconductor gallium nitride (GaN) leads to a large electronic polarization along a unique crystal axis. This makes the two surfaces of the semiconductor wafer perpendicular to the polar axis substantially different in their physical and chemical properties. In the past three decades, the cation (gallium) face of GaN has been used for photonic devices such as light-emitting diodes (LEDs) and lasers.

Nanostars in Highly Si-Doped GaN.

Understanding the relation between surface morphology during epitaxy of GaN:Si and its electrical properties is important from both the fundamental and application perspectives. This work evidences the formation of nanostars in highly doped GaN:Si layers with doping level ranging from 5 × 10 to 1 × 10 cm grown by plasma-assisted molecular beam epitaxy (PAMBE). Nanostars are 50-nm-wide platelets arranged in six-fold symmetry around the [0001] axis and have different electrical properties from the surrounding layer.

Ion implantation of tunnel junction as a method for defining the aperture of III-nitride-based micro-light-emitting diodes.

We report on III-nitride-based micro-light-emitting diodes (µLEDs) operating at 450 nm wavelength with diameters down to 2 µm. Devices with a standard LED structure followed by a tunnel junction were grown by plasma-assisted molecular beam epitaxy. The emission size of µLEDs was defined by shallow He implantation of the tunnel junction region.

Electrically pumped blue laser diodes with nanoporous bottom cladding.

We demonstrate electrically pumped III-nitride edge-emitting laser diodes (LDs) with nanoporous bottom cladding grown by plasma-assisted molecular beam epitaxy on c-plane (0001) GaN. After the epitaxy of the LD structure, highly doped 350 nm thick GaN:Si cladding layer with Si concentration of 6·10 cm was electrochemically etched to obtain porosity of 15 ± 3% with pore size of 20 ± 9 nm. The devices with nanoporous bottom cladding are compared to the reference structures.