(Color online) (a) AFM image of the polished Al-face surface of a near on-axis (0001) bulk AlN substrate. Atomic level steps are clearly seen in the scan. (b) AFM image of an AlN epilayer grown on near on-axis (0001) AlN substrate. (c) AFM images of an AlGaN layer grown on off-axis (0001) AlN substrate, and (d) nearly on-axis (0001) AlN substrate.
(Color online) (a) Schematic diagram of an InAlGaN heterostructure for a UV laser diode grown on a bulk AlN substrate. (b) Photograph of fully processed UV laser diodes fabricated on a 1-cm-diameter wafer of bulk AlN. The wafer contains several hundred gain-guided laser diodes.
(Color online) (a) Room-temperature emission spectra for a InGaN MQW laser diode on AlN substrate for different pulsed current densities below threshold. (b) TE and TM laser diode emission spectra for the same diode operating above threshold.
(Color online) (a) High-resolution emission spectrum for a InGaN MQW laser diode operating slightly above threshold. (b) Room-temperature pulsed light-output vs current characteristic for a laser diode emitting at 371 nm.
(Color online) (a) Room-temperature emission spectra obtained from a series of optically pumped laser devices with different InAlGaN and AlGaN MQW active regions grown on bulk AlN substrates. (b) Threshold power densities for optically pumped lasers grown on sapphire (red dots) and AlN substrates (blue stars).
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