Growth and optical properties of III-nitride semiconductors for deep UV (230–350 nm) light-emitting diodes (LEDs) and laser diodes (LDs)

For the first time, we demonstrated intense ultraviolet (UV) emission at 230–350 nm from III-nitride compound semiconductors grown by metalorganic vapor phase epitaxy (MOVPE). First, we obtained 230 nm-band intense UV emission from AlN/AlxGa1−xN quantum wells (QWs) at 77K. The emission efficiency of AlGaN-based QWs was as high as that of blue light-emitting diodes (LEDs) at low temperature, however, it was not significantly high at room temperature (R.T.). We succeeded in the drastic enhancement of R.T. UV emission, by introducing approximately 5% of In into AlGaN, which was due to the efficient radiative recombination of a localized electron-hole pair in In segregation regions. We obtained the first R.T. intense emission of the 320 nm-band from InAlGaN-based QWs. The emission intensity of the InAlGaN-based QWs was as strong as that of commercially available InGaN QWs at R.T. The carrier confinement in the In segregation region was clearly observed from cathode luminescence (CL) measurement. We also achieved p-type doping into wide-bandgap AlGaN using several new methods and accomplished the first successful operation of a 330 nm-band LED.