Comparison of MISLEDs Made on Si-rich SiO x and SiN x
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1208-O09-20
Comparison of MISLEDs made on Si-rich SiOx and SiNx Chun-Chieh Chen1, Cheng-Tao Lin1, Yi-Hao Pai1, and Gong-Ru Lin1 1 Institute of Photonics and Optoelectronics, and Department of Electrical Engineering, National Taiwan University No. 1 Roosevelt Road Sec. 4, Taipei 106, Taiwan R.O.C. ABSTRACT We compare the turn-on voltage, P-I, and EL responses between the MISLEDs made by Si-rich SiNx and SiOx films. Active layer thickness enlarged from 120 to 360 nm is achieved by lengthening deposition time from 10 to 30 min, which inevitably increases the forward turn-on voltage from 3 to 41 V. We observe that the forward turn-on voltage of SiNx based MISLED is only 10.43 V and that of SiOx based one is 69 V with the same film thickness of 100 nm. The tunneling-based carrier transport mechanism is dominated due to the exponential like V-I behavior, while the tunneling probability is strongly dependent on the height of the barriers between metal/dielectric and dielectric/nc-Si matrices. The P-I slope of SiNx and SiOx based MISLEDs are 1.6 and 115.2 mW/A, respectively. The SiNx MISLED reveals threshold current and voltage of only 4 A and 12 V due to lower barrier height of both ITO/SiNx and SiNx/nc-Si, whereas the threshold current and voltage of SiOx based MISLED are 400 A and 78 V, respectively. In comparison, the higher tunneling current through the SiNx MISLED fails to promote the larger external quantum efficiency of the MISLED, indicating that such lower barriers are not beneficial to the confinement of tunneling carriers and the enhancement of lightemission efficiency. INTRODUCTION Silicon-based light-emitting materials have attracted much attention because of their potential application in all-si based optoelectronic integrated circuits [1, 2]. One of these intriguing materials is the Si/Si3N4-based multilayer structure reported by Tan et al., suggesting that the carrier injection mechanism in this structure is through Frenkel–Poole tunneling [3,4]. Jamei et al. fabricated the nanocrystalline Si LED with Si-ncs buried in TiO2 by plasmaenhanced hydrogenation [5]. High-temperature annealing of Si-rich SiNx wirh buried Si-ncs have also been investigated [6,7]. The tunneling probability of carriers into Si-nes buried in these dielectic matrices is strongly dependent on the barrier height between metal and dielectric layer. In comparison, Si3N4 provides a lower barrier (5.1 eV) than SiO2 (9 eV), allowing more electrons and holes tunneling from metal and p-Si substrate to SiNx at a given bias current. Park et al. reported that the turn-on voltage of their SiNx device having Ni/Au top contact layer was less than 5 V. With an external quantum efficiency of 2 10-3%, this value is higher than similar LEDs made by porous Si [8]. Chen at al. preliminarily reported that the EL efficiency of device with Ca/Ag cathode was about 1.6 10-1 Cd/A [9], and the strong green-yellow EL from SiNx based LEDs was also observed [10]. Up to now, there are few literatures indicated the exact optical power density of SRSN device. Cho repor
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