AlGaN/GaN quantum well (QW) structures are grown on c-plane sapphire substrates by molecular beam epitaxy. Control at the monolayer scale of the well thickness is achieved and sharp QW interfaces are demonstrated by the low photoluminescence linewidth. The QW transition energy as a function of the well width evidences a quantum-confined Stark effect due to the presence of a strong built-in electric field. Its origin is discussed in terms of piezoelectricity and spontaneous polarization. Its magnitude versus the Al mole fraction is determined. The role of the sample structure geometry on the electric field is exemplified by changing the thickness of the AlGaN barriers in multiple-QW structures. Straightforward electrostatic arguments well account for the overall trends of the electric-field variations.

Articles you may be interested inDiffusion of Mg dopant in metal-organic vapor-phase epitaxy grown GaN and AlxGa1−xN Reduction of Mg segregation in a metalorganic vapor phase epitaxial grown GaN layer by a low-temperature AlN interlayer J. Appl. Phys.

A detailed transmission electron microscopy study of pyramidal defects appearing in highly Mg-doped GaN is reported. It is shown that these defects are closed pyramidal inversion domains. From a high-resolution microscopy study, we propose atomic models for inversion domain boundaries which consist of Mg 3 N 2 building blocks for both the basal and inclined facets of the pyramids. In Mg-doped GaN grown by metalorganics vapor phase epitaxy, these pyramidal inversion domains are a few nanometers wide, and their density is high enough to play a role in the free hole density decrease at high Mg doping.

InGaN/GaN self-assembled quantum dots (QDs) were obtained by molecular beam epitaxy making use of the Stranski–Krastanov growth mode. Room-temperature photoluminescence (PL) energy of QDs was observed from 2.6 to 3.1 eV depending on the dot size. PL linewidths as low as 40–70 meV at 10 K and 90–110 meV at 300 K indicate low dot size dispersion. The comparison of PL intensity versus temperature of an InGaN epilayer and InGaN/GaN QDs demonstrates the higher radiative efficiency of the latter.

Europium was implanted into GaN through a 10nm thick epitaxially grown AlN layer that protects the GaN surface during the implantation and also serves as a capping layer during the subsequent furnace annealing. Employing this AlN layer prevents the formation of an amorphous surface layer during the implantation. Furthermore, no dissociation of the crystal was observed by Rutherford backscattering and channeling measurements for annealing temperatures up to 1300°C. Remarkably, the intensity of the Eu related luminescence, as measured by cathodoluminescence at room temperature, increases by one order of magnitude within the studied annealing range between 1100 and 1300°C.

We report on the growth and characterization of green InGaN light-emitting diodes (LEDs) grown on Si (111) substrates using metalorganic vapor phase epitaxy. A single InGaN quantum well active layer has been used. The optical qualities of InGaN on Si(111) and the p–doping efficiency of GaN are discussed. The turn-on voltage of the LED is 6.8 V and the operating voltage is 10.7 V at 20 mA. Electroluminescence of the LEDs starts at a forward bias of 3.5 V. The electroluminescence peaks at 508 nm, with a full-width at half maximum of 52 nm. An optical output power of 6 µW (in ∼ 8π/5 sr) was achieved for an applied current of 20 mA.

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