The effect of optical bandwidth of light-emitting transistors under different size layout design

• Main Authors: Peng-Hao Chou, 周鵬豪
• Other Authors: Chao-Hsin Wu
• Format: Others
• Language: zh-TW
• Published: 2013
• Online Access: http://ndltd.ncl.edu.tw/handle/81075901939545039151

碩士 === 國立臺灣大學 === 光電工程學研究所 === 101 === 　　The invention of light-emitting transistors (LETs) in 2004 has revolutionized the concept of the carrier radiative recombination rate for the past 50 years. It is recognized that the radiative recombination lifetime of the　traditional light-emitting diodes (LEDs) and diode lasers (DLs) are in the nano-second range. However, the pico-second level of recombination lifetime of LETs and transistor lasers (TLs), which can be determined by experiments, provides great potential for next generation optical communication light source. 　　In the thesis, we have designed different sizes of emitter radius hE and base radius hB of InGaP/GaAs LETs in aperture layout design. Through different layout designs, the LETs exhibit different electrical current gain (β = IC/IB) and optical light output due to different carrier recombination processes in the transistor base region and different parasitics. By reducing the lateral emitter radius from 9 to 6.5 μm, β increases due to the higher injection current densities and better confinement of the radiative recombination in the base region. Moreover, β increases when reducing the base radius from 13.5 to 11 μm with fixed emitter diameter. We have obtained multi-GHz spontaneous light modulation of LETs from rf measurement, and the device performance is closely related to different layout designs with different device parasitics under equivalent circuit small-signal model analysis. 　　The intrinsic optical bandwidth, enhanced under the higher base current density, can be also obtained by de-embeding the circuit parasitics effect. Through the analysis of small-signal equivalent circuit models, we have projected the overall optical bandwidth under device lateral scaling, such as E8B27, E8B16, and E5B16. As IB is 2 mA, the intrinsic optical bandwidth of E5B16 is 14 GHz. By the circuit paracistics effect, the overall optical bandwidth would drop to 8.1 GHz, but it still has a great potential to break the record.