Abstract: A photodetector includes a first semiconductor layer, an absorption structure, a second semiconductor layer, and a barrier structure. The absorption structure is located on the first semiconductor layer, and having a first conduction band, a first valence band, and a first band gap. The second semiconductor layer is located on the absorption structure, and having a second conduction band, a second valence band, and a second band gap. The barrier structure is located between the absorption structure and the second semiconductor layer, and having a third conduction band, a third valence band, and a third band gap. The third conduction band is greater than the second conduction band or the third valence band is less than the second valence band.

Abstract: A photo-detecting device includes a first semiconductor layer with a first dopant, a light-absorbing layer, a second semiconductor layer, and a semiconductor contact layer. The second semiconductor layer is located on the first semiconductor layer and has a first region and a second region, the light absorbing layer is located between the first semiconductor layer and the second semiconductor layer and has a third region and a fourth region, the semiconductor contact layer contacts the first region. The first region includes a second dopant and a third dopant, the second region includes second dopant, and the third region includes third dopant. The semiconductor contact layer has a first thickness greater than 50 ? and smaller than 1000 ?.

Abstract: This invention deals with the problem of an error voltage in a MOSFET analog switch sample and hold circuit caused by the turn off charge in the MOSFET analog switch. The invention provides a compensating circuit which can be adjusted to exactly compensate for the turn off charge which causes the error so that the error can be reduced to zero or nearly zero. The compensating circuit can be used in both open loop and closed loop sample and hold circuits. The compensating circuit can be used in combination with a Miller feedback circuit for eliminating the error voltage.