Metalorganic chemical vapor deposition of quaternary AlInGaN multiple quantum well structures for deep ultraviolet emitt
- PDF / 394,352 Bytes
- 6 Pages / 595 x 842 pts (A4) Page_size
- 11 Downloads / 171 Views
Metalorganic chemical vapor deposition of quaternary AlInGaN multiple quantum well structures for deep ultraviolet emitters J. W. Yang, C. Q. Chen, J. P. Zhang, Q. Fareed, H. M. Wang, M. -Y. Ryu, E. Kuokstis, G. Simin, M. A. Khan Department of Electrical Engineering, University of South Carolina, Columbia, South Carolina 29208 Abstract We report on the growth of quaternary AlInGaN layers and MQWs by two different metalorganic chemical vapor deposition (MOCVD) techniques such as pulsed atomic layer epitaxy (PALE) and pulsed MOCVD (PMOCVD). For both growth processes, emission wavelength of quaternary MQWs can be tuned from 350 nm to 300 nm by simply changing the unit growth cell configurations. The PALE grown AlInGaN MQWs have a very smooth surface, few band tail states and exhibit a band-to-band emission. The PMOCVD grown AlInGaN MQWs exhibit a high density of band tail states, which strongly enhance spontaneous emission. Based on the characterization by photoluminescence, X-ray diffraction and AFM, both MOCVD techniques grown quaternary samples are shown to be promising for fabricating the active region of deep UV LEDs. Introduction III-V nitrides are highly promising for application in blue/green and ultraviolet (UV) lightemitting diodes (LEDs) and laser diodes (LDs).1-3 UV light emitting diodes (LEDs) with emission in the range of 300 – 350 nm are ideal for pumping the fluorescent film for full color display devices. It is one of the most promising ways for solid state white lighting. The UV optical devices have additional advantages for high-density optical storage, chemical identification and disposal facilities for industrial waste water. III-V nitride based UV LEDs require the use of high Al-mole fraction AlGaN or quaternary AlInGaN layers as the active region of the devices due to the desired wide direct bandgap. It is difficult to obtain efficient UV emission from ternary high Al content AlGaN quantum wells at room temperature.4,5 Therefore, quaternary AlInGaN layers have received more and more attention for the multiple quantum wells (MQWs) active region of the deep UV LEDs.5-10. In this paper, we reported on the two different metalorganic chemical vapor deposition (MOCVD) techniques, namely, pulsed atomic layer epitaxy (PALE) and pulsed MOCVD for AlInGaN epilayers and MQWs deposition. The resulting AlInGaN layers and MQWS are shown to be promising for UV light emitting application. Experiment The AlInGaN layers were grown on (0001) sapphire substrates using a vertical flow lowpressure metalorganic chemical vapor deposition reactor. Trimethyl-aluminum (TMA), trimethyl-indium (TMIn), triethyl-gallium (TEGa) and ammonia (NH3) were used as the precursors for Al, In, Ga and N, respectively. In order to overcome the growth temperature dilemma for Al content and In content nitrides, two pulsed growth modes, PALE and PMOCVD, were used to deposite the quaternary layers and MQWs around 750-760 °C. In PALE process, AlInGaN layers and MQWs were deposited by repeats of a unit growth cell which was grown by a sequential
Data Loading...
