We have demonstrated 340-nm-band high-output-power InAlGaN quantum well (QW) ultraviolet (UV) light-emitting diodes (LEDs) under room temperature (RT) continuous wave (CW) operation, which were deposited on sapphire (0001) substrates by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). The high-output-power UV LEDs were achieved by introducing p-type InAlGaN layers in order to obtain a high hole concentration and by optimizing the band lineup to suppress electron overflow. The output power of a UV-LED with p-InAlGaN layers was about 4.7 times larger than that of an equivalent structure containing p-AlGaN. We obtained a significant increase in output power by controlling the barrier height of the electron-blocking layer (EBL) and the depth of the quantum wells. We also obtained a marked increase in UV output power by introducing a low-threading-dislocation-density (TDD) AlN buffer layer. The maximum output power and external quantum efficiency (EQE) of LEDs containing p-InAlGaN layers were 8.4 mW and 0.9%, respectively, at an emission wavelength of 346 nm under room temperature (RT) CW operation.

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In order to achieve high‐efficiency ultraviolet (UV) light‐emitting diodes (LEDs), p‐type layers with sufficient hole concentration is quite important to suppress the electron overflow. We introduced Mg‐doped InAlGaN for p‐type layers of the UV‐LEDs for the purpose of obtaining higher hole concentration, and achieved high power CW operations of the UV‐LEDs. 340 nm‐band InAlGaN‐based multi‐quantum‐well (MQWs) UV‐LEDs with Mg‐doped InAlGaN electron‐blocking layer (EBL) and Mg‐doped InAlGaN layers were grown on sapphire substrates by metal‐organic chemical vapor deposition (MOCVD). The output power of UV‐LED with p‐InAlGaN layers was approximately 4.7 times larger than that with p‐AlGaN layers. Maximum output power and the external quantum efficiency (EQE) of the LED with p‐InAlGaN layers were 8.4 mW and 0.9%, respectively, at emission wavelength of 346 nm under room temperature (RT) CW operation. From these results, p‐InAlGaN is shown to be useful for the realization of high‐efficiency UV‐LEDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ballistic electron Surface-emitting cold cathode based on porous polysilicon exhibits excellent performance as a novel flat panel display. It is demonstrated that emission current is stable up to an ambient pressure of 10 Pa. 53(RGB) x 40 pixels multicolour matrix panel is fabricated and evaluated its performance. Fabricating process is mainly based on conventional silicon process and anodisation process, for which we can expect lower production cost at larger panel fabrication.

The use of quaternary InAlGaN is very attractive for the realization of commercially‐available low‐cost and high‐power ultraviolet light‐emitting diodes (UV‐LEDs), because highly‐efficient UV emission can be obtained from this material due to In‐segregation effects. We achieved remarkable improvements in output power from 340 nm‐band quaternary InAlGaN‐based UV‐LEDs and demonstrated high UV‐output power by using high‐quality AlN buffer templates on sapphire substrates. Threading dislocation densities (TDDs) for screw and edge‐type dislocations were 1×108cm–2 and 1×109cm–2, as observed from cross‐sectional transmission electron microscope (TEM) images. The output power of a 340 nm‐band UV‐LED was increased by approximately 7 times by reducing the full‐width‐at‐half‐maximum (FWHM) of the (10‐12) X‐ray ω‐scan rocking curve (XRC) from around 800 arcsec to 510 arcsec. As a result, we achieved a maximum output power of 7.1 mW under room‐temperature (RT) and continuous‐wave (CW) operation. From these results, we confirmed that the crystalline quality of AlN/AlGaN templates strongly affects the output power of UV‐LEDs. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)