Recent advances in ZnO materials and devices

Wurtzitic ZnO is a wide-bandgap (3.437 eV at 2 K) semiconductor which has m any applications, such as piezoelectric transducers, varistors, phosphors, and transparent conducting films. Most of these applications require only p olycrystalline material; however, recent successes in producing large-area single crystals have opened up the possibility of producing blue and W ligh t emitters, and high-temperature, high-power transistors. The main advantag es of ZnO as a light emitter are its large exciton binding energy (60 meV), and the existence of well-developed bulk and epitaxial growth processes; f or electronic applications, its attractiveness lies in having high breakdow n strength and high saturation velocity. optical UV lasing, at both low and high temperatures, has already been demonstrated. although efficient elect rical lasing must await the further development of good, p-type material. Z nO is also much more resistant to radiation damage than are other common se miconductor materials? such as Si, GaAs, CdS, and even GaN; thus, it should be useful for space applications. (C) 2001 Elsevier Science B.V. All right s reserved.