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Semiconductor photodiode
| Details |
Inventors: Miura, Shuichi; Mikawa, Takashi; Kuwatsuka, Haruhiko; Yasuoka, Nami;
Assignee: Fujitsu Limited (Kawasaki, JP)
Primary Examiner: Hille; Rolf
Assistant Examiner: Fahmy; Wael
Attorney, Agent or Firm: Staas & Halsey
An APD includes a substrate formed of n.sup.+ -type Al.sub.x Ga.sub.1-x Sb or Al.sub.x Ga.sub.1-x Sb.sub.y As.sub.1-y semiconductor, whose aluminum content ratio x is typically within a range from 0.1 to 0.3. A light absorbing layer is formed of an-type GaSb semiconductor on the substrate. An avalanche multiplication layer is formed of n-type Al.sub.x Ga.sub.1-x Sb or Al.sub.x Ga.sub.1-x Sb.sub.y As.sub.1-y semiconduct, whose aluminum content ratio x is from 0.02 to 0.1, typically 0.065, so that an ionization rate ratio of positive and negative carriers is essentially maximized by a resonant impact ionization phenomenon. A p.sup.+ -region is formed as a surface layer of n-type Al.sub.x Ga.sub.1-x Sb or Al.sub.x Ga.sub.1-x Sb.sub.y As.sub.1-y semiconductor on the avalanche multiplication layer or directly in the avalanche multiplication layer so as to form a pn junction. Electrodes are formed on the p-type region and the substrate so as to apply a bias voltage to the APD. A light to be detected is injected through the substrate via an opening in the substrate electrode, while producing no carriers therein, into the light absorbing layer. The avalanche multiplication layer generates resonant impact ionization with only the positive carriers from the light absorbing layer, so that low noise and fast operation of the APD is achieved. Furthermore, the APD structure of the invention allows for easy design of an APD. |
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DETAILED DESCRIPTION What is claimed is: 1.
A semiconductor photodiode, comprising: a substrate formed of one of an n-type Al.
sub.
x Ga.
sub.
1-x Sb semiconductor and an n-type Al.
sub.
x Ga.
sub.
1-x Sb.
sub.
y As.
sub.
1-y semiconductor having a first band gap energy, where the aluminum content ratio x is within a range from 0.
1 to 0.
3 and the antimony content ratio y is within a range from 0 to 1, said substrate having a first surface for receiving light having a wavelength within a range of substantially 1.
3 .
mu.
m to 1.
55 .
mu.
m, a second surface, and a light receiving region; a light absorbing layer formed of an n-type GaSb semiconductor on the second surface of said substrate, said light absorbing layer receiving the light passing through said substrate and producing carriers corresponding to the intensity of the received light; a multiplication layer formed of one of an n-type Al.
sub.
x' Ga.
sub.
1-x' Sb semiconductor and an n-type Al.
sub.
x' Ga.
sub.
1-x' Sb.
sub.
y' As.
sub.
1-y' semiconductor, where the aluminum content ratio x' is within a range from 0.
02 to 0.
1, and the antimony content ratio y' is within a range from 0 to 1, said multiplication layer formed on said light absorbing layer, the aluminum content ratio x' in said avalanche multiplication layer being chosen so as to generate an essentially maximum ionization rate ratio of positive holes and electrons by a resonant impact ionization phenomenon; a surface layer formed of one of an n-type Al.
sub.
x" Ga.
sub.
1-x" Sb semiconductor and an n-type Al.
sub.
x" Ga.
sub.
1-x" Sb.
sub.
y" As.
sub.
1-y" semiconductor on said multiplication layer, where the aluminum content ratio of x" is within a range from 0 to 1 and the antimony content ratio y" is within a range from 0 to 1; and an impurity region formed of a p-type semiconductor doped in said surface layer through a surface opposite from said multiplication layer; a first electrode formed on said first surface of said substrate, through which a voltage is applied, said first electrode being shaped so as to allow incidence of the light into the light receiving region of said substrate; and a second electrode formed on said impurity region, through which a positive voltage is applied with respect to the voltage applied to said first electrode
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MEMS 
