Low Frequency Noise of GaN Based Light Emitting Diodes的GaN基光发光二极管的低频噪声.ppt

sawyes@ Optical and Current Noise of GaN-based Light Emitting Diodes Shayla M.L. Sawyer, S. L. Rumyantsev, N. Pala, M. S. Shur, Yu. Bilenko, J. P. Zhang, X. Hu, A. Lunev, J. Deng, and R. Gaska Agenda Introduction and Motivation LED characteristics Experimental Setup Experimental Results Optical Noise Current Noise Conclusions Research Map: A Road Less Traveled Motivation: Applications of UV sources Motivation: Emphasis for LFN Low noise light sources for biological hazard detection systems Signal-to-noise ratio False negative rate False positive rate Biological experiments to study small and slow variations of transmitted or reflected light Light Sources Investigated LED Performance: SET UVTOP? Experimental Setup Experimental Results: Optical 1/f Noise Experimental Results: Optical Noise Experimental Results: Optical Noise First optical Figure-of-Merit, β n is the number of chips connected in series (n=1 for all LEDs studied in this paper) τ is the radiative life-time q is the electronic charge f is frequency. Experimental Results: βvs. Wavelength Experimental Results: Current 1/f Noise At low currents (ILED10-4A), the noise spectra is the superposition of 1/f and generation recombination (GR) noise Experimental Results: Current GR Noise Experimental Results: Current Noise Theory: Noise Model Proposed Mechanism Trap level near one of the bands Estimates Maximum of noise current dependence corresponds to the level occupancy F=2/3. For ωτcF=1 From this equation Nt can be determined Taking for the estimate the lifetime, , in GaN for the LED with the highest GR noise we obtained Nt=7?1015 cm-3 If τ is constant like GR process “B” the trap level position can be found Conclusions Second generation SET UVTOP? LEDs showed reduced current and optical noise The GR noise demonstrated non-monotonic dependence on current, explained by the presence of relatively shallow trap levels in the quantum well The trap level concentra