InGaN multiple quantum wells (MQWs) with green light emission have been grown on GaN stripes oriented
along the [11-20] direction by selective metal-organic vapor phase epitaxy (MOVPE). Several different
window widths were designed in the SiO2 mask. Completed pyramidal InGaN stripes with flat and smooth
{1-101} sidewall were produced on 2-μm windows while trapezoidal stripes with both {1-101} sidewall and
(0001) top surface were obtained on the 5-μm windows. The former has uniform CL emissions at 500 nm on
the {1-101} sidewall and at 550 nm on the narrow ridge. The latter exhibits similar CL emissions at 500 nm
on the sidewall and at 570 nm on the top surface. These wavelength shifts relative to the CL spectrum peak
(450 nm) from the reference region are attributed to thickness enhancement and indium enrichment in
selective MOVPE. The short-wavelength shoulder near 500 nm in the spectrum from the ridge of the
completed pyramidal strip is attributed to overlapping excitation of the sidewall by the SEM incident beam.
We report the structural and optical properties of AlxGa1-xN/AlyGa1-yN quantum wells (QWs) structures grown by gas
source molecular beam epitaxy with ammonia on sapphire (0001) substrates. QWs structures consist of five pairs of
AlyGa1-yN, 0.3xGa1-xN, 0.55
Optically-based chemical and biological sensors require optoelectronic devices with specific emission and detection
wavelength ranges. Semiconductor optoelectronic devices applicable to this sensing are of particular interest due to their
low power consumption, compact size, long lifetime, and low cost. We report the electrical and optical properties of
deep UV p-i-n photodiodes (PDs) based on short period superlattices (SPSLs) of AlN/AlGaN. All device and test
structures are grown by gas source molecular beam epitaxy with ammonia on sapphire and AlGaN/sapphire substrates.
AlGaN/sapphire substrates were grown by stress controlled hydride vapor phase epitaxy (HVPE). The cutoff
wavelength of PDs based on these SPSLs can be varied from 250 to 280 nm by changing the SPSL barrier/well
thickness ratio. For mesa diodes with 150 μm diameter we obtain extremely low dark leakage current of ~ 3 pA/cm2,
and high zero-bias resistance of ~ 6 x 1014 Ω. A cutoff wavelength of 247 nm is obtained for these devices with four
orders of magnitude rejection by 315 nm. We obtain a maximum responsivity of 60 mA/W.
We report the electrical and optical properties of deep ultraviolet light emitting diodes (LEDs) based on digital alloy structures (DAS) of AlN/Al0.08Ga0.92N grown by gas source molecular beam epitaxy with ammonia on sapphire substrates and AlGaN/sapphire templates. AlGaN/sapphire templates were grown by recently developed stress controlled hydride vapor phase epitaxy (HVPE). For DAS with effective bandgap of 5.1 eV we obtain room temperature electron concentrations up to 1x1019 cm-3 and hole concentrations of 1x1018 cm-3. Based on these results we prepared double heterostructure (DHS) LEDs operating in the range of 250 to 290 nm. The emission wavelengths were controlled through the effective bandgap of the active region. The possible ways for increase of LED's efficiency are discussed. We observed significant improvement in the room temperature luminescence efficiency (by factor of 100) of AlGaN quantum wells when a transition growth mode is induced by reduced flux of ammonia. We found that active layer grown on HVPE AlGaN/sapphire substrates have higher luminescence efficiency (by factor of 3) than DAS grown on sapphire.
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