Physics (Internal)

Indium Nitride: The Extreme III-V Semiconductor Material

This event is part of the Biophysics/Condensed Matter Seminar Series.

Since it was discovered in 2002 that InN was in fact a narrow-gap semiconductor material (Egap ~0.65 eV and not 1.89 eV as previously thought), interest in the properties of this material has increased dramatically. However, the physical and electronic structure of InN surfaces and interfaces (and the In-rich InGaN alloys), are difficult to determine due to problems in preparing clean surfaces following growth by plasma-assisted MBE or MOCVD. We have used in-situ atomic hydrogen cleaning to prepare clean, damage-free InN surfaces for study using a range of experimental techniques; high-resolution electron-energy-loss spectroscopy (HREELS), scanning tunnelling spectroscopy (STS) and photoelectron spectroscopy (PES) have been used to study the electronic and chemical properties of the InN(0001) surface. One of the most prominent properties of the native InN surface is the existence of electron accumulation, with a significantly higher electron density than observed in any other III-V semiconductor material (~ 2.5 × 10E13 cm-2). The existence of electron accumulation has been demonstrated by a wide range of techniques, allowing a broad and consistent set of surface space-charge properties to emerge. The unusual band structure property of InN responsible for this is that the conduction band minimum at the gamma-point is located well below the average mid-gap energy. This means that the surface Fermi level simultaneously lies close to the average mid-gap energy and high in the conduction band. The results leading to this conclusion will be discussed in the talk.