Nitride semiconductors and their applications. Part II: Nitride semiconductors. Nitride papers published. Nitride-based semiconductors. A III-V semiconductor in which N is one of the elements. Examples include AlN, GaN, InN, and alloys such as Al x Ga 1-x N.
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Part II: Nitride semiconductors
1971 GaN LED demonstrated (Pankove)
1986 “High” quality GaN grown (Akasaki)
1988 P-type GaN grown (Akasaki); Nakamura starts work on GaN
1990 Two-flow MOCVD system developed (Nakamura)
1991 High quality p-type GaN grown; first pn-junction GaN LED created
1992 ZnSe-CdZnSe blue laser developed (3M)
1993 Commercial blue GaN LEDs introduced (Nichia)
1996 Room temperature nitride LDs developed (Nichia)
1999 Commercial nitride LDs introduced (Nichia)
2004 SONY markets blue laser DVD writers (23 GB/layer)
1. Inability to grow good quality crystals
2. Inability to grow p-type crystals
Nakamura, Harada, and Seno, J. Appl. Phys 58, 2021 (1991)
High quality GaN
Low quality GaN (0.2 mm)
AlN or GaN buffer layer
Charge carriers are spatially separated from the (now) ionized impurity atoms, leading to higher carrier mobilities.
Electrons form a 2-Dimensional Electron Gas (2-DEG).
Current theory: surface donor defects on AlGaN
Concentration of surface defects and transfer of electrons to GaN well is enhanced by strain-induced electric field.
lattice matched non-lattice matched
Semiconductor with no applied field:
With an applied field:
The mobility is a measure of how easily charge carriers respond to an applied electric field.
Electrons are affected by the long-range Coulomb fields of randomly distributed ionized donor atoms.
Phonons are lattice vibrations in a crystal.
(Highest mobility heterostructures have Al fractions of ~10% and barrier thicknesses of ~130 Å)
Confining potential results in quantized energy levels.