| Summary: | 碩士 === 國立成功大學 === 光電科學與工程研究所 === 94 === In this dissertation, the concepts of the Bias Induced Color-tunable Emitters(BICE) was introduced. Simulation software ISE-TCAD was used to simulate different operation modes by different biasing combinations between base, cathode and anode electrodes. It can be observed that a positive voltage bias (V1) is presented between base and cathode electrodes when the device is operated in the Forward Active Mode. The electric current flows into the active region from the cathode located at the bottom of the device. A larger slope of the bandedges at the Multiple Quantum Well (MQW) in the top of active region was observed from the simulation results, which also decreases the carrier collection efficiency of the MQW. Therefore the Single Quantum Well (SQW) in the bottom of active region can collect more carriers than MQW in the top of active region. This results in a
higher luminous intensity from the Single Quantum Well (SQW) in the top of the active region. When the device is operated in the Reverse Active Mode, V1 is negative and the electric current flows into the active region from base in the top of device. The slopes of the bandedges are smaller so the MQW carrier collection is not affected and can collects more carries than the SQW. Therefore, MQW in the top of active region can collect more carriers and has more luminous intensity. The simulation results agree with the results from the experiments reported in the referred journals. This indicates that the simulation can be used to correctly simulate the operation of the actual device.
Based on the previous work, a more detailed analysis for the BICE is studied using the same simulation tool. Different device structures, including the number of the MQW and the distance between MQW and SQW, are examed. The simulation results indicate that a optimized number of the MQW exists, which is a compromised number between two operation modes. Longer distance between two sets of quantum well results in a higher contrast between two operation modes. However, the contrast change becomes insignificant after the distance reaches a certain value. In addition, the position exchange for the MQW and SQW results in a loss of one operation mode.
At the end of this dissertation, a new BICE device structure which have three operation modes is proposed. This new BICE device is capable of emiting three different wavelengths. The three operation modes is controlled by different V1 (V=0, V1>0 and V1<0). A optimized contrast between each mode can be obtained by carefully adjusting the distance between each set of quantum wells.
In conclusion, the operation of BICE is simulated using ISE-TCAD as the simulation tool. We successfully verified the different operation modes from the simulation results. The effect of different device structures on the operation modes were also examed. Finally, a newer design of the BICE device with three operation modes is proposed and the operation is confirmed from the simulation results. Therefore, it is possible to design a BICE device of many operation modes, which is very important for various lighting applications..
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