1.32 μ m InAs ∕ GaAs quantum-dot resonant-cavity light-emitting diodes grown by metalorganic chemical vapor deposition J.Enhanced modulation rate in platinum-diffused resonant-cavity light-emitting diodes J. Appl. Phys. 98, 093504 (2005); 10.1063/1.2125119 Fabrication and characterization of 650 nm resonant-cavity light-emitting diodesIn this article, the authors report on the realization of substrate-free InGaN-based thin-film resonant-cavity light-emitting diodes ͑TF-RCLEDs͒. Experimentally, the sapphire substrate was stripped by using the laser lift-off technique. The / 4-thick Ta 2 O 5 / SiO 2 distributed Bragg reflector and the metallic Ag film with mirror reflectivities of 68% and 97% were, respectively, coated onto the top and bottom of the substrate-free LEDs to form a Fabry-Pérot cavity. The performances of LEDs are characterized by light output power, external quantum efficiency, emission spectrum, angular-resolved intensity distribution, and dynamic response. As a result, the fabricated TF-RCLEDs exhibit a low operating voltage of 3.34 V at 20 mA, a maximum light output power of 6.3 mW at 140 mA, and an external quantum efficiency of 5.5% at 4 mA. In addition, the TF-RCLEDs show temperature insensitivity as compared to the normal LEDs directly grown on the sapphire substrates. Furthermore, the 50% viewing angle of TF-RCLED is smaller than that of normal LED, i.e., 146°versus 168°at 60 mA. Finally, the eye pattern of the TF-RCLEDs is improved compared to that of the normal LEDs as operated at the data transmission rate of 100 Mbit/ s. These results exhibit that the InGaN-based TF-RCLEDs are excellent candidates for the use in short-distance plastic optical fiber communications.
In this study, the laser lift-off (LLO) technique is used to fabricate the substrate-free InGaN thin-film solar cells (TF-SCs). The epitaxial structures consist of 8-pair Ino.23Gao.77N/GaN multiple-quantum-well (MOW), which is sandwiched between the p-and n-GaN to construct the conventional p-i (intrinsic layer)-n solar cells. After the LLO process to remove the sapphire substrate, a silver layer with reflectivity of 97% was deposited onto the bottom of cell to act as the metallic reflector. Under forward bias operation, the fabricated TF-SCs exhibit a low operating voltage of 3.34 V along with an ideality factor of 6 V. Both of which are comparable to their counterparts that reveals the electrical property of device does not damage after the LLO process. On the other hand, it is observed that the spectral response of the InGaN solar cells changes significantly as the incident wavelength below 510 nm. This wavelength corresponds to the energy transition (-2.43 eV) between the first electron and hole energy level of the Ino.23Gao.77N/GaN well. Since part of the unabsorbed photons can be re-reflected by the bottom reflector, the TF-SCs show the enhanced photoresponse as compared to the normal solar cells with the sapphire substrate. Finally, the conversion efficiency of the TF-SC is 1.6 times larger than the normal InGaN solar cell under one sun AM 1.5G spectrum.
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