Material Characterization of Semiconductor Devices

The full-scale progression of optical communications was triggered by the indication in 1966 of the possibility of using low-loss optical fibers for communications. Since then, optical communication technologies have advanced by the development of optical semiconductors such as the laser diode (LD) and photodiode (PD), along with highspeed semiconductor circuit technologies, including the laser driving circuits and integrated circuits for transmission signals; optical fibers used in the development of such technologies have losses of 0.2 dB/km or lower. This has allowed even residential users access to high-speed optical transmission lines as fast as 1 Gbps. The low-loss wavelength band of an optical fiber is in the 1.3 to 1.6 μm band, and InP materials are used for compound semiconductors that are compatible with this range of wavelengths. Since around 1980, light emitting diodes (LEDs), PDs, and LDs have been developed using InP semiconductors. By using the compound semiconductor wafers that have been developed since 1961, such as GaAs and InP, we launched the development of semiconductor devices in the late 1970s, which led to the development of systems and devices for the optical communication industry (1). The development of these semiconductor devices required analytical characterization techniques, for instance, to verify the behavior of the added impurity and the composition and structure of the devices so as to improve the design of the manufacturing process. However, the analysis technology during the 1980s was not satisfactory for the measurement of the active layers that were micrometers to nanometers in thickness and micrometers in width. This necessitated the development of more sophisticated and accurate analysis technologies to solve problems related to device characteristics and reliability. This paper reports on the development of materials for semiconductor devices, as well as reliable technologies that are based on the latest developments in the field of material analyses. 2. Development of Ohmic Contact for P-type InP