Photodetection

Abstract

Embodiments of the present disclosure provide systems, devices, and methods for photodetection. For example, briefly described, in one embodiment among others, a sensor comprises an array of photodetectors, wherein the reflectance of each of the photodectors is a function of the number of photons incident on the respective photodetector; and an electrical insulator positioned between one of the photodetectors and another one of the photodetectors to reduce diffusion of electrons therebetween.

Therefore, at least the following is claimed: 
     
         1 . A sensor comprising:
 an array of photodetectors, wherein the reflectance of each of the photodectors is a function of the number of photons incident on the respective photodetector; and   an electrical insulator positioned between one of the photodetectors and another one of the photodetectors to reduce diffusion of electrons therebetween.   
     
     
         2 . The sensor of  claim 1 , wherein the electrical insulator is at least one of silicon dioxide, a via trench, and a metal coupled to ground. 
     
     
         3 . The sensor of  claim 1 , wherein at least one of the photodetectors includes gallium doped silicon carbide. 
     
     
         4 . The sensor of  claim 1 , wherein the each photodetector includes a doped region of an intrinsic semiconducting material. 
     
     
         5 . The sensor of  claim 4 , wherein the intrinsic semiconducting material is one of silicon carbide (SiC), gallium nitride (GaN), silicon (Si), and gallium arsenide (GaAs). 
     
     
         6 . The sensor of  claim 4 , wherein the intrinsic semiconducting material is doped with at least one of the following dopants: gallium (Ga), boron (B), aluminum (Al), indium (In), and thallium (Tl). 
     
     
         7 . The sensor of  claim 1 , wherein the photodetector includes at least two acceptor energy bands, each energy band being associated with a respective one of two dopants. 
     
     
         8 . The sensor of  claim 7 , wherein the energy difference between the two acceptor energy bands corresponds to photons having a frequency of about 5 terahertz or about 2.5 terahertz. 
     
     
         9 . The sensor of  claim 7 , wherein at least one of the photodetectors is biased to promote at least some of the electrons in a valence energy band in the least one of the photodetectors to one of the two acceptor energy bands. 
     
     
         10 . The sensor of  claim 1 , further comprising an array of avalanche photodiodes, wherein each avalanche photodiode includes a respective one of the photodetectors. 
     
     
         11 . The sensor of  claim 10 , wherein each avalanche photodiode is reverse biased. 
     
     
         12 . The sensor of  claim 1 , wherein at least one of the photodetectors is doped to absorb photons having a frequency of about 5 terahertz or about 2.5 terahertz. 
     
     
         13 . The sensor of  claim 1 , wherein an optically-transparent conductive film is positioned on at least one of the photodetectors. 
     
     
         14 . The sensor of  claim 1 , wherein the photodetector is laser doped. 
     
     
         15 . The sensor of  claim 1 , further comprising an array of vertical cavity surface emitting lasers (VCSELs), each VCSEL including a respective one of the photodetectors as a Bragg reflector. 
     
     
         16 . The sensor of  claim 1 , further comprising an array of laser sources and an array of photodiodes, each photodiode including a respective one of the photodetectors. 
     
     
         17 . The sensor of  claim 16 , wherein each laser source is coupled in parallel to a respective one of the photodiodes. 
     
     
         18 . The sensor of  claim 17 , wherein each laser source is coupled in series to a respective one of the photodiodes. 
     
     
         19 . The sensor of  claim 1 , wherein the array includes a first plurality of photodetectors doped to absorb photons corresponding to a first frequency and a second plurality of photodetectors doped to absorb photons corresponding to a second frequency. 
     
     
         20 . A method of sensing photons, the method comprising:
 reflecting a portion of a laser beam using a photodetector;   absorbing a plurality of photons incident upon the photodetector, thereby increasing a carrier concentration of the photodetector; and   reflecting a greater portion of the laser beam using the photodetector responsive to the absorption of the photons.   
     
     
         21 . The method of  claim 20 , further comprising transmitting the laser beam to the photodetector. 
     
     
         22 . The method of  claim 20 , further comprising detecting a power associated with the reflected portion of the laser beam using a power meter. 
     
     
         23 . The method of  claim 22 , further comprising detecting an increase in the power with the reflected greater portion of the laser beam to a power meter. 
     
     
         24 . The method of  claim 20 , further comprising redirecting the reflected laser beam to the power meter using a dichroic mirror. 
     
     
         25 . The method of  claim 20 , wherein the photodetector includes gallium doped silicon carbide. 
     
     
         26 . A system comprising:
 a sensor including a photodetector, wherein the reflectance of the photodetector is a function of the number of photons absorbed by the photodectector; and   a power meter configured to measure changes in a power of a laser beam reflected by the photodetector.   
     
     
         27 . The system of  claim 26 , further comprising a dichroic mirror that redirects the reflected laser beam to the power meter. 
     
     
         28 . The system of  claim 26 , wherein the photodetector includes gallium doped silicon carbide. 
     
     
         29 . The system of  claim 28 , wherein the sensor further comprises:
 a converter layer deposited on the photodetector, and   an attenuator layer deposited on the converter layer.   
     
     
         30 . The system of  claim 29 , wherein the converter layer includes an n-type wide bandgap material having a high capture cross section. 
     
     
         31 . The system of  claim 29 , wherein the attenuator layer attenuates the velocity of incident particles or radiation. 
     
     
         32 . The system of  claim 29 , wherein the sensor further comprises an absorber layer deposited on the attenuator layer. 
     
     
         33 . The system of  claim 29 , wherein the absorber layer includes at least one of zirconium dioxide (ZrO 2 ), W 2 O 3 , boron carbide (BC), boron nitride (BN) and gadolinium carbide (GdC) 
     
     
         34 . A laser resonator comprising:
 a reflective mirror;   a photodetector positioned opposite the reflective mirror;   a lasing medium positioned between the reflective mirror and the photodetector, wherein the reflectance of the photodector is a function of the number of photons absorbed by the photodetector, and an intensity of a laser beam emitted by the laser resonator is a function of the reflectance of the photodetector.   
     
     
         35 . The laser resonator of  claim 34 , wherein the photons are transmitted to the laser resonator through a dichroic mirror, and the dichroic mirror redirects the laser beam emitted by the laser resonator. 
     
     
         36 . The laser resonator of  claim 34 , wherein the photodetector includes gallium doped silicon carbide. 
     
     
         37 . A method of laser doping an intrinsic semiconducting material, the method comprising:
 providing a semiconducting material having a lattice; and   transmitting a laser beam to the semiconducting material in the presence of a dopant carrying gas carrying a dopant, the laser beam driving the dopant into the lattice of the semiconducting material.   
     
     
         38 . The method of  claim 37 , further comprising communicating a carrier gas from a carrier gas source to a bubbler, the bubbler including a dopant liquid. 
     
     
         39 . The method of  claim 38 , wherein the carrier gas includes at least one of the following inert gases: argon, helium, nitrogen, neon, krypton, xenon, and radon. 
     
     
         40 . The method of  claim 38 , further comprising forming carrier gas bubbles in the dopant liquid using the bubbler. 
     
     
         41 . The method of  claim 40 , further comprising forming the dopant carrying gas from the carrier gas bubbles in the dopant liquid. 
     
     
         42 . The method of  claim 37 , wherein the semiconducting material is provided in a processing chamber, the method further comprising communicating the dopant carrying gas from a bubbler to the processing chamber. 
     
     
         43 . The method of  claim 37 , wherein the dopant is gallium and the semiconducting material is silicon carbide. 
     
     
         44 . A method of fabricating a vertical cavity surface emitting laser (VCSEL), the method comprising:
 providing an intrinsic semiconducting material having a top surface and a bottom surface;   doping the intrinsic semiconducting material to form a photodetector;   depositing at least one epilayer on the top surface of the doped intrinsic semiconducting material;   depositing a quantum well layer on the at least one epilayer;   depositing a buffer layer on the quantum well layer;   forming a pattern layer on the bottom surface of the intrinsic semiconducting material;   wet etching the intrinsic semiconducting material according to the pattern layer, wherein the at least one epilayer provides an etch stop for wet etching the intrinsic semiconducting material, wherein the wet etching forms a cavity;   depositing a distributed Bragg reflector layer in the cavity; and   depositing an optically-transparent conductive film on the distributed Bragg reflector layer to form a p-side contact.   
     
     
         45 . The method of  claim 44 , wherein the intrinsic semiconducting material is silicon carbide. 
     
     
         46 . The method of  claim 44 , wherein the at least one epilayer includes an Al x Ga (1-x) N epilayer, wherein x is within 0.7-0.2. 
     
     
         47 . The method of  claim 46 , wherein the at least one epilayer also includes a GaN epilayer. 
     
     
         48 . The method of  claim 47 , wherein the at least one epilayer also includes an AlN epilayer. 
     
     
         49 . The method of  claim 44 , wherein the quantum well layer includes InGaN. 
     
     
         50 . The method of  claim 44 , wherein the buffer layer includes GaN. 
     
     
         51 . A system comprising:
 a sensor including an array of photodetectors that form a focal plane array, wherein at least one of the photodetectors includes gallium-doped silicon carbide; and   a light emitting diode (LED) positioned to receive light transmitted by the sensor.   
     
     
         52 . The system of  claim 51 , further comprising: a midwave infrared (MWIR) lens, wherein the sensor is positioned to receive light transmitted through the MWIR lens. 
     
     
         53 . The system of  claim 51 , wherein the LED is coupled to a plate, wherein the plate includes at least two pinholes, and light transmitted through one of the pinholes is received by the LED. 
     
     
         54 . The system of  claim 53 , wherein a first lens is positioned between the sensor and the plate. 
     
     
         55 . The system of  claim 53 , wherein a charge coupled device (CCD) is positioned to receive light transmitted through the other pinhole of the plate. 
     
     
         56 . The system of  claim 55 , wherein the charge coupled device (CCD) is positioned to receive light transmitted through the other pinhole of the plate, wherein a second lens is positioned between the plate and the CCD.