Band gap energy

In a semiconductor, insulator, or metal, electrons surrounding the nucleus are present in energy levels with a certain width. In semiconductors or insulators, among the energy bands where electrons exist, the highest energy band filled with electrons at absolute zero degrees is called the valence band, and the energy band with no electrons is called the conduction band. The energy range in the band gap (forbidden band) between the valence band and the conduction band is called the band gap energy. In metals, there is no band gap because the valence band and conduction band overlap each other.

Bias angle - Microchannel plate

The bias angle of a microchannel plate is the angle between the channel wall and a line perpendicular to the input plane. The detection efficiency of an MCP for charged particles and electromagnetic radiation can be optimized by controlling the angle of incidence of the input event. Typical bias angles range from of 5° to 15°.

Bias T

A circuit used to apply a DC bias to a device. This circuit is capable of applying a DC bias while maintaining an impedance match and is therefore needed when using a high-speed device.

Bi-phase signal

An encoding method of modulating signals so that “0” signals or “1” signals will not occur in consecutive 3 bits or more. Compared to NRZ signals, bi-phase signals have two-fold redundancy and the bandwidth usage efficiency is 50%. As one example, a 25 Mbps bi-phase signal is equivalent to an NRZ signal of 50 Mbps. Bi-phase signals offer the advantage that they can extract clock components by using a simple circuit. Other encoding methods similar to bi-phase signals include CMI (coded mark inversion) and Manchester encoding.

Bit error rate

This is one measure for evaluating the transmission quality of digital transmissions. It indicates the probability that the transmitted codes may be incorrectly identified. The bit error rate is intimately related to the S/N, but there are cases where the bit error rate is not determined just by the S/N.


A phenomenon in which the photoelectrically converted signal charge in an image sensor exceeds a certain level and spills over into adjacent pixels or transfer region other than photodiodes (in IT type CCDs). In CCDs, the spill-out charge appears in the image as a vertical stripe occurring from thelight incident position the same as with “smear.” To prevent blooming, some means for discharging excess charge should be implemented. In CCDs, this blooming is suppressed by using a vertical/horizontal anti-blooming or clocking method.

Bragg diffraction

A coherent, strong reflection that occurs at a particular angle at which the phases are matched by multiple surface reflections when monochromatic light strikes a light-scattering material with a cyclically arranged structure. This technique is utilized to fabricate resonators in semiconductor lasers.

Breakdown voltage

As the reverse voltage applied to a PN junction is raised, an abrupt increase in reverse current occurs at a certain voltage. This voltage is called the breakdown voltage. As a guide for convenience when evaluating our Si APD, the voltage that produces a reverse current of 100 uA is specified as the breakdown voltage.

Bump bonding

A technology for fabricating bumps (metal protrusions such as solders) on a semiconductor wafer. Bump bonding is used for three-dimensional mounting, and the fine-pitch bumps make devices smaller and more sophisticated.