Low Frequency Noise Study On GaN-based Light Emitting Diodes

As a typical type of semiconductor material of the third generation, Gallium Nitride has a lot of special properties,so it has been demonstrated a large potential for applications in electronic devices of irradiation-hardness,high-frequency,large-power and superintegration,and also in optoelectronic devices,such as blue,green and violet light emitting diodes and photodetectors.While as a new semiconductor material, because of a variety of material physics and technoloical problems introduced in the devices preparation, they contain high value of defects density and their quality and reliability is far less than Si and GaAs,whose technologies are matured. Their noise level has a relationship with inner defects,directly influences the divices'performances,applications and reliability. So study on GaN-based material and devices'noise will be helpful to probe defects in these devices, especially to inspect the influence of latent defects on the devices'performances.Here are the main contributions and conclusions of this paper:1) The results of experimental and theoretical studies of GaN-based materials and devices and their low-frequency noise are reviewed first. Bying researching the structure,preparation technologies and operation principles of GaN-based light emitting diodes, we thoroughly analyzed the factors that influence the quality and the performance of GaN-based light emitting diodes.2) Low frequency noise of GaN-based light emitting diodes was successfully tested within a wide range of bias currents. Experimental results demonstrate that its low frequency noise contains mainly 1/f noise, the amplititude of the 1/f noise is proportional to bias current ( I ) in the range below 5×10?5A,while, in the current range above 5×10^-5A, the magnitude the 1/f noise is proportion to I 2. We also compared the low frequency noise of GaN-based light emitting diodes with that of GaAs-based light emitting diodes.3) By analyzing the generation mechanisms of the low frequency noise of GaN-based light emitting diodes and investigating the relationship of the magnitude of the 1/f noise with the bias currents,we determined the different noise mechanisms under different current transportion conditions,proposed three related 1/f noise models based on the mechanisms of carriers number fluctuation and mobility fluctuation.4) By testing the low frequency noise of the irradiated devices, at low current levels,the spectrum very often contains a Lorentzian spectrum component on top of the 1/ f noise due to g-r noise and the maginitude of this noise component increases as the total doses increases,we also give a tentative explanation.The 1/ f noise can be separated into two noise components: fundmental 1/ f noise and nonfundmental 1/ f noise. Last,we chose the maginitude of nonfundmental 1/ f noise as a device's reliability representation parameter.The work done in this paper provides an experimental and theoretical basis for 1/f noise to be used in characterizing reliability of GaN-based Light emitting diodes.