Summary of the invention
The objective of the invention is to, a kind of structure of quantum cascade detector that existing photovoltaic type quantum well Infrared Detectors is surveyed mechanism that is different from is provided.The thinking of existing photovoltaic type infrared quantum well detector is to separate formation polarization potential with the magazine center by photoelectron to produce photovoltaic voltage, and the present invention provides unidirectional electron transport by special step-like band structure design, thereby produce the photovoltaic electric current, therefore has stronger photovoltaic response, and have higher device resistance and lower noise and power consumption, and the forceful electric power-phonon interaction in the quanta cascade detector makes the excitation electron relaxation time short more a lot of recombination time than interband.Thereby the quanta cascade detector has higher detectivity and better frequency performance than conventional guide type quantum well detector and existing photovoltaic type infrared quantum well detector.Aspect working temperature, quanta cascade detector of the present invention has reached working and room temperature under certain wavelength.
The invention provides a kind of structure of quantum cascade detector, comprising:
One substrate;
Ohmic contact layer once, this time ohmic contact layer is produced on the substrate, realizes ohmic contact with electrode material thereby this time ohmic contact layer carries out high-concentration dopant;
One potential barrier separator, this potential barrier separator is produced on down the middle part on the ohmic contact layer, and what make down ohmic contact layer forms table top all around, and this potential barrier separator undopes;
One multiply periodic active area structure layer, this multiply periodic active area structure layer is produced on the potential barrier separator, and this multiply periodic active area structure layer is the core position of realizing the detection photoelectric current of detector;
Ohmic contact layer on one, ohmic contact layer is produced on the multiply periodic active area structure layer on this, thus ohmic contact layer carries out high-concentration dopant and realizes ohmic contact with electrode material on this;
One top electrode, this top electrode is produced on the ohmic contact layer;
One bottom electrode, this bottom electrode are made in down on the ohmic contact layer table top all around.
The material of wherein said substrate is GaAs or indium phosphide.
One side of the bottom surface of wherein said substrate forms the inclined-plane of one 45 degree.
The wherein said material of ohmic contact layer down is GaAs or indium gallium arsenic.
The material of wherein said potential barrier separator is GaAs or indium gallium arsenic.
The periodicity of wherein said multiply periodic active area structure layer is 10-50.
Each periodic structure of wherein said multiply periodic active area structure layer is made up of a plurality of quantum well, each quantum well is isolated by the barrier layer of different-thickness, first quantum well is the wideest, and carry out high-concentration dopant, the optical excitation transition takes place in electronics in this trap, second and later quantum well all undope, and second quantum well is the narrowest, and quantum well width is subsequently widened gradually until the width near first quantum well.
The material of the quantum well in each periodic structure of wherein said active area structure layer is GaAs or indium gallium arsenic, and the material of barrier layer is gallium aluminium arsenic or indium aluminium arsenic.
The wherein said material of going up ohmic contact layer is GaAs or indium gallium arsenic.
Embodiment
See also shown in Figure 1ly, the invention provides a kind of structure of quantum cascade detector, comprising:
One substrate 10, the material of this substrate 10 is GaAs or indium phosphide, one side of the bottom surface of this substrate 10 forms the inclined-plane of one 45 degree, and this is because the sub-band transition of quanta cascade detector can only absorb the TM polarization components of incident light, vertical this 45 degree inclined-plane incident of incident light;
Once ohmic contact layer 20, this time ohmic contact layer 20 is produced on the substrate 10, realizes and the ohmic contact of electrode material that the material of this time ohmic contact layer 20 is GaAs or indium gallium arsenic thereby this time ohmic contact layer 20 carries out high-concentration dopant, be doped to silicon doping, concentration is generally 1 * 10
18Cm
-3
One potential barrier separator 30, this potential barrier separator 30 is produced on down the middle part on the ohmic contact layer 20, and what make down ohmic contact layer 20 forms table top all around, and this potential barrier separator 30 undopes, the material of this potential barrier separator 30 is GaAs or indium gallium arsenic, and thickness is generally 2-5nm;
One multiply periodic active area structure layer 40, this multiply periodic active area structure layer 40 is produced on the potential barrier separator 30, this multiply periodic active area structure layer 40 is the core positions of realizing the detection photoelectric current of detector, the periodicity of this multiply periodic active area structure layer 40 is 1050, the periodicity of present embodiment is 30, each periodic structure of this multiply periodic active area structure layer 40 is made up of a plurality of quantum well, each quantum well is isolated by the barrier layer of different-thickness, first quantum well is the wideest, and carry out high-concentration dopant, the optical excitation transition takes place in electronics in this trap, second and later quantum well all undope, second quantum well is the narrowest, quantum well width is subsequently widened gradually until the width near first quantum well, the material of the quantum well in each periodic structure of this active area structure layer 40 is GaAs or indium gallium arsenic, and the material of barrier layer is gallium aluminium arsenic or indium aluminium arsenic;
Ohmic contact layer 50 on one, should go up ohmic contact layer 50 is produced on the multiply periodic active area structure layer 40, thereby should go up the ohmic contact that ohmic contact layer 50 carries out high-concentration dopant realization and electrode material, the material that should go up ohmic contact layer 50 is GaAs or indium gallium arsenic, be doped to silicon doping, concentration is generally 1 * 10
18Cm
-3
One top electrode 60, this top electrode 60 is produced on the ohmic contact layer 50;
One bottom electrode 70, this bottom electrode 70 are made in down on ohmic contact layer 20 table top all around.
40 design considerations of active area structure layer and the method for designing of the above-mentioned structure of quantum cascade detector that provides below are provided in detail.To survey wavelength is that the quanta cascade detector of 10.7 μ m is an example, and as shown in Figure 2, the active area band structure of the one-period of quanta cascade detector is designed to: first quantum well is the silicon doping quantum well, and doping content is 4.5 * 10
17Cm
-3, this quantum well is the wideest, and width is
Second quantum well undopes, and this quantum well is the narrowest, and width is
Third and fourth quantum well all undopes, and width widens gradually, is respectively
With
Four potential barrier thickness are respectively
With
Because the first excited state in first quantum well and second adjacent with it quantum well ground state level height overlap, therefore light activated electronics enters the ground state of second quantum well from the first excited state of first quantum well by tunnelling.Widen gradually because quantum well trap subsequently is wide, the interval of the ground state energy of adjacent quantum well forms one by one the energy step near a long vertical optical phonon, the optical excitation electronics is by forceful electric power-phonon interaction, get back to the doped quantum well of next cycle with similar form of the getting out of a predicament or an embarrassing situation relaxation that releases energy rapidly, behind the doped quantum well that arrives next cycle, described optical excitation process before repeating.Survey the quanta cascade detector of wavelength for other, the quantum well in the active
area structure layer 40 and the width of potential barrier and quantity are by surveying the wavelength decision.
The aforesaid unidirectional shuttling movement of electronics makes the quanta cascade detector that lasting photoelectric current can be provided, and this photo-signal intensity is greater than existing photovoltaic type infrared quantum well detector.This brings a lot of benefits: first when surveying, and the quanta cascade detector, only need amplify photoelectric current without any need for external bias voltage as the current source that photoelectric current is provided, and has therefore simplified test circuit greatly.The second, the detection performance of quanta cascade detector only is subjected to the restriction of thermal noise, because the noise of the dark current that thermal noise causes than extra electric field is little a lot, thereby the quanta cascade detector has better noise characteristic.The 3rd, dark current makes the electric capacity of reading circuit reach capacity easily, and therefore the time of integration of guide type infrared focal plane array is shorter usually.And the electric current of quanta cascade detector mainly is a photoelectric current, and its infrared focal plane array can reach the very long time of integration, and imaging is more clear.The 4th, owing to do not need extra electric field, quanta cascade detector power consumption is little, and it is low to generate heat, and has higher temperature resolution.The 5th, the quanta cascade detector is based on the sub-band transition band of bound state in the active trap to bound state, so the detecting light spectrum live width is narrow, thereby has reduced the interference of background emission, has further improved the noiseproof feature of quanta cascade detector.The 6th, it is short more a lot of recombination time than interband that strong electronics-phonon interaction makes the electronics relaxation time of intersubband in the quanta cascade detector, and there is not the carrier accumulation effect, therefore quanta cascade detector operation frequency can reach very high in theory, is suitable as very much the high speed optoelectronic device.
Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.