In this thesis, microlens and InP/InGaAs heterojunction bipolar phototransistor are first investigated and integrated. The microlens is fabricated on the back-side of InP substrate and the radius curvature of lens is optimized to focus light on the absorption layer. The effect of integration of microlens and HPT is confirmed by using three different measurements. The three types of measurement methods are front illumination, back illumination and illumination through back-side lens.
When the light with a wavelength of 1.55μm is illuminated on the back-side of HPT, the HPT has 2 times higher photocurrent than the HPT using front illumination method has. The increase is owing to reduction of the reflection on the contact metal and interconnection line by using back-illumination method. The HPT utilizing back-side microlens has 0.61A/W responsivity(PD mode) while the dc responsivity of back illuminated HPT is 0.18A/W(PD mode). Coupling efficiency improvement is 34.8%. Fiber alignment range is wider by introducing back-side microlens. When fiber is placed at 22μm away from center, the HPT without lens has 31% of its maximum current value while the HPT with lens has 73% of its maximum value.
InP/InGaAs 포토트랜지스터와 마이크로렌즈가 처음으로 집적되었다. 렌즈의 곡률 반경은 빛이 흡수층에 초점이 맞추어지도록 설계되고 제작되었다. HPT를 윗면 입사한 경우 보다 뒷면으로 입사하였을 때 광 전류가 두 배 이상 증가하였다. 렌즈가 있는 경우 렌즈가 없는 경우 보다 광 전류가 3배 이상 증가 하였다. 또한 렌즈가 있을 경우 파이버의 정렬면에서 유리하다는 것이 입증되었다.