Characteristic Temperature Estimation for GaN-Based Lasers
- PDF / 620,373 Bytes
- 6 Pages / 417.6 x 639 pts Page_size
- 76 Downloads / 157 Views
for GaN-Based Lasers T. Honda', H. Kawanishi*, T. Sakaguchi*, F. Koyama** and K. Iga** *Department of Electronic Engineering, Kohgakuin University, 2665- i Nakano-machi, Hachiohji-shi, Tokyo 192-0015, Japan e-mail: ctl 1761 @ns.kogakuin.ac.jp TEL:+81-426-22-9291 ext. 3440 FAX: +81-426-25-8982 **Precision and Intelligence Laboratory, Tokyo Institute of Technology 4259 Nagatsuta, Midori-ku, Yokohama 226-8503, Japan Cite this article as: MRS Internet J. Nitride Semicond. Res. 4S1, G6.2 (1999) Abstract We have estimated the characteristic temperature To of GaN-based vertical-cavity surfaceemitting lasers. The density matrix theory including intraband relaxation broadening has been taken into account. The estimated To is about 300 K, which suggests a good temperature characteristic in GaN-based lasers. Introduction Gallium nitride (GaN) and related compounds have large bandgap energies and are attractive for light-emitting devices operating in blue to ultraviolet spectral regions [i ,2}. Recently, room temperature pulsed operation of GaN-based laser diodes (LDs) has been reported [31. In these reports, it was shown that the introduction of a quantum well (QW) structure as an active layer is very effective for realizing the GaN-based laser. The characteristic temperature of lasers is one of the important parameters for applications such as to optical memories, from the viewpoint of hightemperature operation. A less sensitive temperature is preferable for wide-ranging applications. In this paper, we report the estimation of temperature sensitivity for a GaN-based laser with a quantum well structure as the active layer. The internal quantum efficiency of GaN QW layers is one of the important issues in terms of low power consumption and operation reliability. In the first step, carrier confinement in a GaN QW layer is estimated. G6.2 Mat. Res. Soc. Symp. Proc. Vol. 537 ©1999 Materials Research Society
Carrier Confinement Ratio We have assumed the equilibrium condition in a single QW structure and defined the confinement ratio as a function of the density of states, as shown in the following equation.
R,.o,,j - -- N2o
(1)
N2D + N3D
Where, Rconf, N2Dand N3D are the confinement ratio, number of carrier in a QW layer and barrier layers, respectively. In this estimation, we have assumed a quantum well with a finite offset. The
density of states in the single QW layer (2-dimensional), g2D(E) and the barrier layer (3dimensional), g3D(E) can respectively be written as [4]
,3
g2o(E), =•2 •.-•-T-)
•
(2t
3
(2m)•, •-_• g•u ( E ) = 2--•3 ( •/ E
)
(3)
The total carrier concentration, Nrot in the QW and barriers is expressed as
N'o' = I {g2o( E) + g3D( E)}f ( EEs )dE.
(4)
Where, f(EEf) is Fermi distribution function. From eqs. (1) - (4), we can derive the equation of the carrier confinement ratio. The confinement ratio of the GaN/A1GaN QW structure as a function of the injected carrier density is shown in Fig. 1. We also show that of the GaAs/AIGaAs QW for comparison. We assumed that the band offset ratios of AEc/AEv ar
Data Loading...
