InGaN/GaN/AIGaN-Based Laser Diodes With an Estimated Lifetime of Longer Than 10,000 Hours
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Introduction GaN and related materials, such as AlGalnN, are Ill-nitride semiconductors The etching depth was as great as 2 uxa direct energy band structure which is suitable for light-emitting devices. At present, the main focus of Ill-nitride semiconductor research is the realization of a current-injected laser diode which is expected to be the shortest-wavelength semiconductor laser diode (LD) produced.
Short-wavelength-emitting devices, such as blue LDs, are currently required for a number of applications, including fullcolor electroluminescent displays, laser printers, read-write laser sources for high-density information storage on magnetic and optical media, and sources for undersea optical communications. Major developments in wide-gap III nitride semiconductors have recently led to the commercial production of highbrightness blue/green light-emitting diodes (LEDs)1 and to the demonstration of room-temperature (RT) violet laser light emission in InGaN/GaN/AlGaNbased heterostructures under pulsed and continuous-wave (cw) operations.1"6 The lifetimes of the InGaN multi-quantumwell (MQW)-structure LDs have improved to 300-1,150 h under conditions of RT-cw operation.7'8 However further improvements of the LD characteristics, including lifetime, are required to enable the commercialization of shortwavelength LDs. Currently, growing the thick AlGaN cladding layer required for optical confinement is difficult, due to the formation of cracks during growth. These cracks are due to the stress introduced in the AlGaN cladding layers caused by lattice mismatch, and the difference in thermalexpansion coefficients between the AlGaN cladding layer and GaN layers. In the case of a thin AlGaN layer, the elastic strain is not relieved by the formation of
Jacques Pankove's Pioneering Contribution to the Field of Nitride Semiconductors 77K Nitride Semiconductors Symposium of the 1997 Fall Meeting of the Materials Research Society was dedicated to Jacques Pankove of Astralux, Inc. for his pioneering work in development of the field of wide bandgap nitride semiconductors. The following is extracted from 1. Akasaki's (Meijo University) presentation, published in the MRS Proceedings Volume 482, which also describes the background from which Shuji Nakamura's work grew.
The rapid development of technology based on nitride semiconductor research must have surprised everybody. It may appear that everything could be achieved within such a short period of time. But this would be a big mistake because it did not start just three fiscal years back in time! No, we have to go back as far as 1970, down to Princeton, to find the scientist of the first hour, Jacques Pankove, studying the luminescence properties of GaN. Light emission has ever been on Pankove's mind. In 1956 in Paris, he was challenged with the idea to use a pn-junction to inject a population inversion in a semiconductor to make a laser. To achieve this, Pankove first studied luminescence in Ge for his PhD
MRS BULLETIN/MAY 1998
dissertation in 1960. Then he fabricated the
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