Photodetector having high speed and sensitivity

Patent · Tue Jan 01 04:00:00 EST 1991

OSTI ID:867998

Morse, Jeffrey D ^[1]

---

1. Martinez, CA

The present invention provides a photodetector having an advantageous combination of sensitivity and speed; it has a high sensitivity while retaining high speed. In a preferred embodiment, visible light is detected, but in some embodiments, x-rays can be detected, and in other embodiments infrared can be detected. The present invention comprises a photodetector having an active layer, and a recombination layer. The active layer has a surface exposed to light to be detected, and comprises a semiconductor, having a bandgap graded so that carriers formed due to interaction of the active layer with the incident radiation tend to be swept away from the exposed surface. The graded semiconductor material in the active layer preferably comprises Al.sub.1-x Ga.sub.x As. An additional sub-layer of graded In.sub.1-y Ga.sub.y As may be included between the Al.sub.1-x Ga.sub.x As layer and the recombination layer. The recombination layer comprises a semiconductor material having a short recombination time such as a defective GaAs layer grown in a low temperature process. The recombination layer is positioned adjacent to the active layer so that carriers from the active layer tend to be swept into the recombination layer. In an embodiment, the photodetector may comprise one or more additional layers stacked below the active and recombination layers. These additional layers may include another active layer and another recombination layer to absorb radiation not absorbed while passing through the first layers. A photodetector having a stacked configuration may have enhanced sensitivity and responsiveness at selected wavelengths such as infrared.

• Research Organization: Lawrence Livermore National Laboratory (LLNL), Livermore, CA
• DOE Contract Number: W-7405-ENG-48
• Assignee: United States of America as represented by United States (Washington, DC)
• Patent Number(s): US 5051804
• OSTI ID: 867998
• Country of Publication: United States
• Language: English

Related Subjects

/257/
1-x
1-y
absorb
absorb radiation
absorbed
active
active layer
additional
additional layer
additional layers
adjacent
advantageous
bandgap
below
carriers
carriers formed
combination
comprise
comprises
configuration
defective
detected
due
embodiment
embodiments
enhanced
enhanced sensitivity
exposed
exposed surface
formed
gaas
gaas layer
graded
grown
incident
incident radiation
included
infrared
interaction
layer
layer comprises
layer grown
layers
light
material
passing
photodetector
positioned
positioned adjacent
preferably
preferably comprise
preferably comprises
preferred
preferred embodiment
process
provides
radiation
recombination
responsiveness
retaining
selected
selected wave
selected wavelength
selected wavelengths
semiconductor
semiconductor material
sensitivity
speed
stacked
stacked configuration
sub-layer
surface
swept
temperature
temperature process
tend
time
visible
visible light
wavelengths
x-rays