Study on New Emitter Structure Using Ultra-Thin Silicon Carbide Films as Hole Blocking Layr

可以通过引入比基极区域更宽的能量带隙发射极来减小基极电阻。这可以提高双极晶体管的工作速度。我们提出了非晶碳化硅（a-SiC）和微晶硅（mu - c-Si）作为发射极材料，并使用它们制作了原型器件。当器件只使用c-Si时，由于外延生长形成Si同质结，器件的电流增益较低。然而，我们在沉积c-Si薄膜之前先用a- sic超薄薄膜制备器件，得到的电流增益比c-Si器件大20-30倍。然而，a-SiC器件的发射极电阻增加，降低了高频性能。接下来，我们尝试制造具有SiGe基作为窄带隙基的器件。用氩离子束溅射Si和Ge靶材形成SiGe薄膜。加入Ge后，外延温度降低。例如，Si_<.75>Ge_<.25>的外延温度低至400 C。此外，我们利用电子回旋共振（ECR）等离子体CVD方法研究了低温硅外延生长。在薄膜生长过程中，不仅有沉积过程，还有蚀刻过程。发现后一种工艺对增强外延生长是有效的。此外，通过控制沉积条件，成功地实现了选择性外延生长。

It is possible to reduce the base resistance by introducing wider energy bandgap emitter than a base region. This can make operation speed of bipolar transistor faster. We proposed amorphous SiC (a-SiC) and microcrystalline Si (mu c-Si) for the emitter material and fabricated prototype devices using those. For only using mu c-Si the device showed low current gain because of epitaxial growth which forms the Si homojunction. Whereas, we fabricated devices with a a-SiC ultra-thin film before deposition of a mu c-Si film, resulting in 20-30 times larger current gain than that of the mu c-Si device. However emitter resistance of the a-SiC device increased, which degraded high frequency performance.Nextly, we attempted to fabricate devices having SiGe base as a narrow bandgap base. SiGe films were formed by sputtering Si and Ge targets using an Ar ion beam. Epitaxial temperature went down by adding Ge. For example, the epitaxial temperature was as low as 400ﾟC for composition of Si_<.75>Ge_<.25>.Furthermore, we investigated low temperature Si epitaxial growth by ECR (Electron Cycrotron Resonance) plasma CVD method. In the film growth process, not only deposition process but also etching process was found to proceed. The later process was found to be effective for enhancing epitaxial growth. Moreover, selective epitaxial growth was successfully carried out by controlling the deposition conditions.