III-N Multiple Quantum Wells Based 280-340 nm Deep Ultraviolet Light Emitting Diodes over Sapphire

摘要

High power deep ultraviolet (UV) light emitting diodes (LEDs) are good candidates for solid-state lighting, bio-chemical detection and short-range communications. In this paper we describe the progress from our and other research groups towards fabricating 340-280 nm LEDs. In past we have reported on deep UV LEDs on sapphire substrates with active region comprised of pulsed atomic layer epitaxy (PALE) deposited quaternary AlInGaN and ternary AlGaN multiple quantum wells (MQWs). These studies indicated a key role played by current crowding (thermal effects), active region design (polarization effects) and the base material quality (active region defects originating from buffer AlGaN layers) in controlling the emitted powers. Now using a unique AlGaN/AlN superlattice to control strain we have deposited Si-doped high Al-content n~+-AlGaN layers over sapphire with thickness in excess of 2 μm. These layers and a new active layer design have yielded high power deep UV LEDs with emission wavelength from 280-340 nm. For 325 nm emission devices powers as high as 10 mW for 1 A pulsed pump current and 1 mW for 100 mA dc pump current were measured. For 280 nm emissions a power of 0.47 mW for 260 mA dc and 3 mW for 1 A of pulsed pump current was measured. For III-N deep UV LEDs, these values to date represent devices with the highest powers for the shortest wavelengths. In this paper we present the details of material and device fabrication and characterization. Initial data on device life-tests are also presented.