Deep-diffused phototransistor

A large area planar deep-diffused phototransistor for detecting incident radiation when biased at a selected biasing voltage, said phototransistor comprising:

• a transistor block having a first surface and a second surface, said second surface being disposed opposite to said first surface;
• a light entry layer comprising a p type semiconductor material, said light entry layer further comprising said first surface, said p type semiconductor material comprising said light entry layer having a deep diffused positive doping gradient in accordance with a deep diffused doping profile such that the concentration of the p type dopant is greater closest to said first surface;
• a respective well comprising neutron transmutation doped silicon n type semiconductor material having a resistivity in the range between about 20 .OMEGA.-cm and 200 .OMEGA.-cm, the doping concentration of said n type semiconductor material comprising said well layer being substantially constant therethrough, said well extending from a well-portion said second surface into said light entry layer such that a deep diffused first p-n junction is formed therebetween along a collector-base boundary of said well, said first p-n junction comprising a parallel segment aligned substantially parallel to said first surface, said well portion of said second surface being surrounded on said second surface by a respective transistor isolation portion of said light entry layer so as to electrically isolate said well along said second surface, each respective first p-n junction further comprising an oblique segment disposed between the respective parallel segment of said first p-n junction and said block second surface such that said p-n junction is disposed at an oblique intercept angle with respect to the plane of said second surface at the intersection between said first p-n junction and said second surface;
• and
• a respective readout contact comprising a p type semiconductor material disposed in each of said respective wells, each of said readout contacts extending into said respective wells from said second surface;
• said light entry layer, said respective well, and said respective readout contact comprising a collector region, a base, and an emitter, respectively, of said phototransistor;
• each of said phototransistors further comprising a photosensitive region having an area of not less than about 1 mm.sup.2 and having a base width is selected such that the capacitance of said device is in a range between about 0.5 pf/mm.sup.2 and 2 pf/mm.sup.2,
• the effective base width of each of said phototransistors when biased at said selected biasing voltage is in the range between about 3 .mu.m and 50 .mu.m, each of said wells further comprising a depletion layer when biased at said selected biasing voltage having a thickness in the range between about 30 .mu.m and 200 .mu.m.

A planar deep-diffused large area phototransistor array for detecting incident radiation when biased at a selected biasing voltage, said phototransistor array comprising:

• an array block having a first surface and a second surface, said second surface being disposed opposite to said first surface;
• a light entry layer comprising a p type semiconductor material, said light entry layer further comprising said first surface of said array block;
• a well layer comprising an n type semiconductor material, said well layer being disposed in contact with said light entry layer such that a deep diffused first p-n junction is formed therebetween along a collector-base boundary of said well aligned substantially parallel to said first surface, said well layer further comprising respective well-portions said second surface;
• and
• for each phototransistor in said array, a respective readout contact comprising a p type semiconductor material extending into said well layer from said second surface;
• said light entry layer, said well layer, and said respective readout contact comprising a collector region, a base, and an emitter, respectively, of said phototransistor;
• each of said phototransistors further comprising a photosensitive region having an area of not less than about 1 mm.sup.2.