Ultra High-Speed Operation of Ultra-Fine GaInAs/InP HBT by Suppressing Recombination Current at Mesa Sidewall

HBT台面侧壁复合电流的测量干法/湿法腐蚀法制备的精细发射极采用电子束曝光、CH_4/H_2反应离子刻蚀和湿法刻蚀相结合的方法，可以制作100 nm宽的精细发射极。比较了这种精细HBT和以前的湿法腐蚀HBT的电流增益随尺寸的变化关系。在用HCl和CH3COOH腐蚀液组合实现发射极侧壁为010的HBT中，干/湿联合腐蚀工艺使其电流性能达到或超过仅用湿法腐蚀所获得的电流性能，并实现了电流增益大于50%，足以满足电路应用的要求。因此，我们可以看出，即使在具有精细发射极的HBT中也可以实现优异的电流性能。采用精细发射极和金属线集电极制作高速HBT。精细发射极结构与降低基极集电极电容的方法相结合，可以减小基极集电极电容，从而实现HBT的快速工作。因此，我们在亚微米宽发射极HBT中引入了一种基极集电极电容降低的方法，即采用埋入金属线作为集电极。结果表明，在发射极宽度为0.3微米、长度为1.5微米的器件中，基极集电极电容小于0.1fF是已报道的最小值，并获得了200 GHz的最大振荡频率f_t；max&gt；由于目前器件的性能在很大程度上受到器件的非本征部分的限制，例如，当我们引入另一个研究小组报告的布线技术时，HBT的高速工作是可以预期的。

Measurement of Mesa Sidewall Recombination Current of HBT with Fine Emitter Fabricated by Combination of Dry/Wet EtchingIt has been enabled to fabricate 100 nm wide fine emitter by a combination of electron beam exposure, CH_4/H_2 reactive ion etching and wet etching. Size dependence of current gain of this fine HBT has been compared with that of formerly fabricated HBT only by wet etching. In HBT with 010 emitter sidewall realized by a combination of HCl and CH_3COOH etching solution, dry/wet combination etching process has enabled to obtain current performance even or superior to that obtained by only wet etching and current gain over 50, which is sufficiently large for circuit application, has been realized. Therefore, we could show excellent current performance could be realized even in HBT with fine emitter.Fabrication of High-Speed HBT with Fine Emitter and Metal Wire CollectorFine emitter structure combined with reduction method of base-collector capacitance can reduce base-collector capacitance, and therefore, can realize fast operation of HBT. So, we have introduced a base-collector capacitance reduction method, where buried metal wire has been used as collector, to HBT with sub-micron wide emitter. As results, in a device with an emitter having a width of 0.3 um and a length of 1.5 um, a base-collector capacitance less than 0.1 fF, which is the smallest value among ever reported, has been confirmed and a maximum oscillation frequency f_<max> of 200 GHz has been also achieved. Since at present the device performance is largely restricted by non-intrinsic part of the device, such as contact resistance, a more high-speed operation of HBT can be expected when we introduce, for example, a wiring technique reported by another research groups.