Li-Wei Tu ^[*] , Ching-Lien Hsiao and Min-Hsiung Tsai
Department of Physics and Center for Nanoscience and Nanotechnology,
National Sun Yat-Sen University, Kaohsiung, Taiwan 80424, Republic of C hina

Although the laser head of the next generation DVD and the blue/green and white light emitters are all made from nitrides, hot debate on the fundamental band gap energy of InN has just begun starting from successful growth of high quality materials. In year 2002, several reports showed experimental evidence of a band gap of smaller than 1 eV as compared with 1.9 eV in previous literatures. Values in the range of ~ 0.6 - 0.8 eV are most commonly seen in recent works. This discovery opens up a whole new territory in the potential applications of optoelectronics. Together with other nitrides semiconductors, InN, GaN, and AlN cover a complete energy spectrum from infrared to ultraviolet. But, up to now, there are still so many unresolved important issues from growth to device fabrications. No one can predict what the final scenario will be, yet, more challenges motivate more research activities. In this short article, a brief overview of the current status on InN is given. Critical issues are discussed while mysteries remain to be resolved.