Influence of metal–semiconductor interface treatments and absorber structure on the performance and reliability of uni-traveling-carrier photodiodes (UTC-PDs)
摘要
The effects of absorber structure–controlled by adjusting the thickness ratio of doped and undoped InGaAs layers–and metal-semiconductor interface treatment methods were investigated in waveguide-type UTC-PDs. Ultraviolet-ozone (UVO) and ammonia solution cleaning of the InGaAs surface improved the interface quality in terms of contact resistivity and bias-temperature stability. Nevertheless, devices cleaned using buffered oxide etchant (BOE) exhibited higher photoresponsivity and superior frequency characteristics. This phenomenon is attributed to the reduction of dark current (IDark) caused by the residual interfacial oxide layer at the metal/InGaAs interface. In contrast, the influence of absorber structure variation was negligible. These results demonstrate that the interface condition plays a more dominant role than absorber modification in determining device performance. Therefore, optimizing the interface condition while maintaining a high-quality oxide layer is essential for further enhancing UTC-PD performance.