Wide-band-gap III-nitride semiconductors

Article By:

Han, Jung Yale University, New Haven, Connecticut.

Nurmikko, Arto V. Brown University, Providence, Rhode Island.

Last reviewed:2005

DOI:https://doi.org/10.1036/1097-8542.YB051530

The band gap, or more precisely energy band gap, denotes the difference in energy between the highest valence electron energy states (valence band maximum) and the lowest conduction energy states (conduction band minimum). In optoelectronic devices, the band gap dictates the wavelength of light that a semiconductor absorbs and emits. The size of band gap also determines the ultimate robustness of electronic devices under high ambient temperature or excessive power loads. Semiconductors, including II–VI compounds, such as ZnSe, ZnS, and ZnO, have at times shared the label of wide-band-gap semiconductors by providing important proof-of-concept demonstrations of blue-green lasers and light-emitting diodes (LEDs) in the early 1990s. In a relatively short time, however, the nitride compounds with three of the column IIIA elements (AlN, GaN, and InN) have emerged as exceptionally versatile semiconductors, with functionalities unattainable from traditional Si and GaAs technologies. Compared to GaAs with an energy gap corresponding to infrared emission (890 nanometers), the AlGaInN family covers the entire visible spectrum from infrared (InN) to blue (InGaN), and extending into deep ultraviolet (AlGaN), creating opportunities in display, illumination, high-density optical storage, and biological and medical photonics (Fig 1). Performance of traditional Si devices is known to deteriorate at device temperatures above 100°C (212°F) or when the applied voltage exceeds certain critical electrical fields. Transistors and diodes made from wide-band-gap GaN are expected to create opportunities beyond low-power digital electronics, including applications in automobiles, aircraft, utility distribution, and wireless communications.

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