JOURNAL OF LIGHTWAVE TECHNOLOGY, VOL. 26, NO. 13, JULY 1, 2008 1891 Fabrication and Characterization of Temperature Insensitive 660-nm Resonant-Cavity LEDs Jun-Rong Chen, Tsung-Shine Ko, Tien-Chang Lu, Member, IEEE, Yi-An Chang, Hao-Chung Kuo, Senior Member, IEEE, Yen-Kuang Kuo, Jui-Yen Tsai, Li-Wen Laih, and Shing-Chung Wang, Life Member, IEEE, Fellow, OSA Abstract—InGaP/AlGaInP 660-nm resonant-cavity light-emit- ting diodes (RCLEDs) with stable temperature characteristics have been achieved by extending the resonant cavity length from one optical wavelength to three optical wavelengths and tripling the number of quantum wells. When the operation temperature increases from 25 C to 95 C, the degree of power variation at 20 mA is reduced from 2.1 dB to 0.6 dB for the conventional 1- cavity RCLEDs and 3- cavity RCLEDs, respectively. In order to interpret the temperature-dependent experimental results, advanced device simulation is applied to model the RCLEDs with different cavity designs. According to the numerical simulation results, we deduce that the stable tem- perature-dependent output performance should originate from the reduction of electron leakage current and thermally enhanced hole transport for the 3- cavity AlGaInP RCLEDs. Index Terms—Leakage current, modeling, polymethyl methacrylate plastic optic fiber (POF), resonant-cavity light-emit- ting diode (RCLED), semiconductor device. I. INTRODUCTION R ESONANT-CAVITY light-emitting diodes (RCLEDs) have been adopted as ideal light sources for optical interconnects due to several inherent advantages including enhanced output intensities, narrow spectral linewidth, im- proved beam directionality, high modulation bandwidth, and thresholdless operation [1], [2]. Especially, RCLEDs oper- ating at near 660 nm have become a key component for the application in short-distance data communication system due to a minimum attenuation loss of 0.15 dB/m at 650 nm in the polymethyl methacrylate plastic optical fibers (POFs) [3]. Manuscript received December 3, 2007; revised January 22, 2008. Published August 29, 2008 (projected).This work was supported by the MOE ATU program and in part by the National Science Council of the Republic of China under Contracts NSC 95-2120-M-009-008, NSC 95-2752-E-009-007-PAE, NSC 95-2221-E-009-282, and NSC 95-2112-M-018-007. J.-R. Chen, T.-S. Ko, T.-C. Lu, H.-C. Kuo, and S.-C. Wang are with the Department of Photonics and Institute of Electro-Optical Engi- neering, National Chiao Tung University, Hsinchu 30050, Taiwan, R.O.C. (e-mail: jrchen.eo95g@nctu.edu.tw; tsko.eo93g@nctu.edu.tw; timtclu@fac- ulty.nctu.edu.tw; hckuo@faculty.nctu.edu.tw; scwang@cc.nctu.edu.tw). Y.-A. Chang was with the Department of Photonics and Institute of Electro- Optical Engineering, National Chiao Tung University, Hsinchu 30050, Taiwan, R.O.C.. He is now with the Millennium Communication Co., Ltd., Hsinchu 303, Taiwan, R.O.C. (e-mail: rayman0313.eo92g@nctu.edu.tw). Y.-K. Kuo is with the Department of Physics, National Changhua University of Education, Changhua 50058, Taiwan, R.O.C. (e-mail: ykuo@cc.ncue.edu. tw). J.-Y. Tsai and L.-W. Laih are with the Millennium Communication Co., Ltd., Hsinchu 303, Taiwan, R.O.C. (e-mail: jytsai@m-comm.com.tw; lwlaih@m-comm.com.tw). Digital Object Identifier 10.1109/JLT.2008.920639 Conceptually, a typical RCLED consists of two distributed Bragg reflectors (DBRs) and an active layer located between two mirrors. In a conventional light-emitting diode (LED), only about 4% of light is escaped from the surface of LED due to the large refractive index of semiconductors. As compared to conventional LEDs, the resonant cavity of RCLED forces the light to emit into the radiation cone for a certain wavelength instead of isotropic emission. Furthermore, when the thickness of the resonant cavity is shortened to be only several optical wavelengths, the effect of photon quantization in this micro- cavity will enhance spontaneous emission properties. For more details about RCLEDs, the reader can refer to the related review paper [4]. Further applications of RCLEDs and POFs have been de- veloped to the automotive industry, such as media oriented systems transport (MOST), which needs to carry 50–250 Mb/s of data over POFs. Therefore, higher temperature-stable output performance is required for AlGaInP RCLEDs applied in this field. One of the most important approaches to improve the temperature-dependent performance is the engineering of gain cavity resonance alignment. Specifically, the cavity mode is often intentionally designed to be at a slightly longer wavelength relative to the peak gain at room temperature. As the device is heated with the increasing injection current, the peak gain shifts into alignment with the cavity mode to provide optimum RCLED performance. However, the device temperature increases with increasing operating current. It can be expected that the RCLED output power is limited by the temperature-induced misalignment at higher operating temperatures. Consequently, the gain cavity alignment within an RCLED can be engineered to obtain low temperature-insen- sitive performance at a particular temperature range. Based on this engineering technology, Hild et al. reported the AlGaInP RCLEDs with a less temperature sensitivity over the temper- ature range from 15 C to 75 C by employing the design of a large gain cavity detuning [5]. Nevertheless, they found that the prevalence of electron leakage reduces the output efficiency with increasing operation temperature [5]–[7]. Furthermore, several high-performance AlGaInP RCLEDs have been re- ported in recent years. The demonstrated properties include high output power [8], high external quantum efficiency [9], low operation voltage [10], high emission directionality [11], and high modulation bandwidth [12]–[15]. Although signifi- cant progress in AlGaInP RCLEDs has been achieved under room temperature operation, it is still necessary to improve the temperature-dependent output performance as the injection current and operation temperature increase. As compared to 0733-8724/$25.00 © 2008 IEEE