In this work, three approaches are proposed to implement high-speed 850-nm optical receivers fully in standard bulk
0.18 μm silicon (Si) CMOS technology. In the first approach, the lateral p-i-n photodiode (PD) with designed block well
to limit the photocarriers being generated from the laterally depleted regions is integrated in optical receiver. The
receiver consists of TIA, LA, offset-cancellation-network and buffer to provide a conversion gain of 110 dBΩ and data
rate of 2.5 Gbps operation. In the second receiver, the spatially modulated PD (SMPD) with -3 dB bandwidth of 590
MHz is integrated in optical receiver with the extra adaptive equalizer and demonstrates a data rate of 3.125 Gbps.
Finally, the proposed novel structure of PD eliminates the slow diffusion photocarriers by using body contact design to
create a new current path under the PD. A bandwidth of 2.8 GHz with 100 % improvement in PD is obtained. The eye
diagrams of PD with cable connected amplifiers at 2.5 Gbps, 4 Gbps and 5 Gbps are demonstrated. Furthermore, the
optical receiver's optical-electrical (O-E) conversion bandwidth is also increased from 3.6 GHz to 4.3 GHz. To our
knowledge, these are the highest O-E conversion bandwidth of the PD and optical receiver ever reported by using the
standard bulk 0.18 μm Si CMOS technology.
We have investigated the thermal stability of three composite metals on their contact resistivities and luminous intensities for using as the reflector in flip-chip light-emitting diode (FCLED). The composite metals were simultaneously deposited on <i>n</i>-type GaN without alloy to form <i>n</i>-type Ohmic contact and simplify the process. The investigated composite metals were Ti/Al/Ti/Au (30/500/30/300 nm), Cr/Al/Cr/Au (30/500/30/300 nm) and Cr/Ti/Au (500/30/300 nm), respectively. The specific contact resistivity of Ti/Al/Ti/Au, Cr/Al/Cr/Au and Cr/Ti/Au on the <i>n</i>-type GaN Ohmic contact were changed from 5.4×10<sup>-4</sup>, 6.6×10<sup>-4</sup> and 7.7×10<sup>-4</sup> Ω-cm<sup>2</sup> to 5.3×10<sup>-4</sup>, 4.5×10<sup>-4</sup> and 1.3×10<sup>-4</sup> Ω-cm<sup>2</sup> respectively after 500 hours thermal stress at 150°C in the air. After 96 hours of thermal stress, the luminous intensities at 20 mA of these three structures were decreased 6.2%, 11.1% and 1.4%, respectively. Therefore, in addition to maintain good n-type ohmic contact and simplify the process, the Cr/Ti/Au composite metal demonstrates good thermal stability as a reflector in FCLED.