The Maruska group demonstrated violet luminescence recently using a similar structure doped with Mg atoms to achieve high resistance in a top layer.The luminescence was considered due to the radiative recombination of electrons at deep accepters in the insulating region of GaN, which were created due to ionization by high electric field. The development of group III-nitride has been held back for several years due to poor-quality material prepared usingcurrently available growth techniques. Moreover, the irreproducibility of the result was a major concern.
The progress in group III-Nitride resumed in the early 1980s after good quality precursors, along with modern growth technologies such as metal-organic chemical vapour deposition (MOCVD) and Molecular Beam Epitaxy (MBE). The breakthrough was in the field was accomplished by Akasaki group, in the year of 1991, by achieving highest hole concentration up to the order of sixteen in GaN. Which led the development of first p-n junction UV light-emitting diode.The availability of good quality precursors and modern characterization techniques in the 1990s enabled researchers to develop new ways of fabricating device structures based on group III-Nitrides. In the year of 1994, Nakamura group reported the first high bright blue LED, using In GaN/AlGaN double-heterostructures. Since then, the development of light-emitting device shifted towards the use of multiple quantum wells (MQW) as an active region in light emitting diodes (LEDs) and laser diodes (LDs). In 1996, Nakamura group demonstrated the very first violet In GaN MQW based laser diode.HEMTs in Group III-Nitrides were not new back then, as GaAs/AlGaAs heterostructures had been demonstrated in the 1980s. GaN and related alloys, which have inherent polarization, could theoretically be used for high mobility devices. However, it was hard to find good quality materials until the 1990s. In the late ‘90s, a considerable amount of effort was made in the field of group III-nitride materials, which enhanced our understanding and resulted in the development of commercially available technologies. It was the year of 1991-92 when M. A. Khan's group observed the first 2DEG in GaN/AlGaN heterostructure, the mobility of which was 834 cm2/Vs at room temperature. In addition, the M. A. Khan group demonstrated the first GaN/AlxGaN heterostructure grown by MOCVD. The electron mobility of this heterostructure was reported to be twelve time higher at room temperature as compared to bulk GaN of the same thickness. These achievements paved the way for the application of III-Nitride materials in power electronics. In the current market, GaN HEMT devices with ratings between 0.65 -1.2 kV are availableAlthough, we have come a long way and have enriched our understanding in the field of group III-Nitrides the full potential of these semiconductors has not been utilized yet. Still structural and electronic properties and growth mechanism need further exploration and investigation. The above said fundamental limitation in our understanding is delaying some of the potential applications of group III-Nitrides.