MXPA98000205A - Photodetectors using nitrides ii - Google Patents

Abstract

A photodetector which is a nitride III-V and having predetermined electrical properties is described, the photodetector includes a substrate with interdigitalized electrodes formed on its surface, the substrate has a sapphire base layer, a layer of pH regulator formed from of a III-V nitride and an individual crystal III-V nitride film, the three layers are formed by molecular beam epitaxy facilitated by electron cyclotron electron resonance plasma, the use of the molecular beam epitaxy procedure facilitated by microwave plasma of electron cyclotron resonance allows to control and predetermine the electrical properties of the photodetect

Description

PHOTODETECTORS USING III-V NITRIDES Portions of this invention were made with the support of the government of the United States, under the concession No. DE-FG02-9 ER81843, granted by the Department of Energy; and the government may have certain rights in the invention.

FIELD OF THE INVENTION This invention relates to photodetectors. More specifically, this invention relates to photo ethers suitable for use in the detection of radiations having wavelengths shorter than those of the visible spectrum.

BACKGROUND OF THE INVENTION Photodetectors are widely defined as devices that respond to incident electromagnetic radiation, converting the radiation to electrical energy, which allows to measure the intensity of the incident radiation. Typically, a photodetector includes a certain kind of photoconductor device and external measurement circuits. Photodetectors have many applications. For example, photodetectors have use in scientific research (such as in flash detectors) in manufacturing (such as in devices to detect and prevent that products are spoiled by contamination with light) and in security applications (as in the prevention of excessive exposure of workers to certain radiations). In many applications it is convenient to detect a particular type of light, that is, a certain scale of wavelengths. In said application, light having a wavelength that is outside the wavelength scale to be detected constitutes "noise" for the photodetector. Noise may cause a wrong response from the photodetector. UV photodetectors of the prior art have the drawback that they typically respond to visible light.

BRIEF DESCRIPTION OF THE INVENTION It is an object of the present invention to solve these drawbacks and others of the prior art. It is an object of the present invention to provide a photodetector of ultraviolet (UV) light that is "blind" to visible light. Another objective of the present invention is to provide a UV photodetector manufactured using III-V nitrides, preferably GaN. According to one embodiment, the present invention comprises a photoconductive device comprising GaN, which is preferably deposited on a substrate by means of molecular ray epitaxy assisted by microwave plasma, resonance in electronic cyclotron (ERM assisted by RCE). The deposited GaN includes a buffer layer deposited on the substrate and a monocrystalline film deposited on the buffer layer. The electrical properties of the device are controlled by varying the parameters of the deposition process. A photodetector according to an embodiment of the present invention comprises a GaN device having predetermined electrical properties and first and second electrodes deposited on a surface of the device; the second electrode of the first being spaced. A voltage source is connected through the first and second electrodes to create an electric field within the device. When it is working, when the surface of the device on which the electrodes are deposited is subjected to a photon emission, electron-hole pairs are created inside the device and a flow inside the device, due to the electric field. In another embodiment, the present invention comprises a method for forming a photodetector having predetermined electrical properties. The method comprises manufacturing a GaN device to control the electrical properties of the device; depositing a first electrode on a surface of the device and depositing a second electrode on the surface of the device; being spaced the second electrode of the first. In yet another step, a voltage source is connected through the first and second electrodes.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of an ERM development chamber aided by RCE. Figure 2a is an X-ray diffraction pattern of a GaN film on sapphire (11-20) developed from a one-step process. Figure 2b is an X-ray diffraction pattern of a GaN over sapphire film (11-20), developed from a two-step process. Figure 3 is a schematic illustration of the device for introducing impurity in the GaN films. Figure 4 is a sectional view of a modality of an ERM development chamber aided by RCE. Figure 5 (a) is a schematic illustration of the flow of magnetic field lines emanating from a source of RCE that has no external solenoid. Figure 5 (b) is a schematic illustration of the flow of magnetic field lines emanating from an RCE source when an external solenoid is used, according to one aspect of the present invention. Figure 6 is a graph showing the effects of the variations in the magnet current for an external solenoid, and the relative ionic density in the substrate. Figure 7 is a graph showing the I-V characteristics of a Langmuir probe operating in a device according to an aspect of the invention. Figure 8 is a schematic illustration of an effusion cell outlet opening, in accordance with an aspect of the present invention. Figure 9 is a graph illustrating an optical emission spectrum for a nitrogen plasma source of RCE. Figure 10 is a graph illustrating an optical emission spectrum for an RCE nitrogen plasma source, which operates with an output aperture according to an embodiment of the present invention. Figure 11 is a graph illustrating the relative intensity of ion emission as a function of the nitrogen flow rate and the opening size of an RCE device, in accordance with an aspect of the present invention. Figure 12 is a sectional illustration of an example of a GaN device of type n. Figures 13 (a) - (c) illustrate surface morphologies of films developed in accordance with the present invention using a source of RCE operating at different microwave powers. Figure 14 schematically illustrates a photodetector circuit in accordance with one embodiment of the present invention. Figure 15 is a graph illustrating the variation in the resistivity of the GaN sample with the power of the microwaves used in the ERM process aided by RCE. Figure 16 is a graph illustrating the dependence of (μt) on the resistivity of the GaN sample. Figure 17 is a graph illustrating a spectral response for a photodetector according to the first embodiment of the present invention. Figure 18 illustrates a developmental structure by which a gallium nitride semiconductor can be produced. Figure 19 is a graph illustrating a spectral response of a bandpass photodetector. Figure 20 is a graph illustrating the response of a GaN detector to the X-ray photons, as a function of the energy of the X-ray photon at a pulse voltage of 100 V.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES Wide bandgap semiconductors, such as III-V nitrides (ie, GaN, InN, A1N) are useful for the production of UV detectors because their large band gap energies provide low noise and blind detection in visible light. III-V nitrides are an attractive class of materials for optoelectronic devices because they form a continuous alloy system, whose direct banned bands range from 1.9 eV (InN) to 3.4 eV (GaN) to 6.2 eV (A1N). Thus, III-V nitrides allow the fabrication of a blind photodetector in visible light and offer the potential to manufacture optical devices that are sensitive to a wide range of electromagnetic radiation, from red to ultraviolet and, possibly, X-rays. In addition, they have high speeds of electronic drift saturation, high thermal stability and are physically and chemically robust. One embodiment of a photodetector 1, according to the present invention, is illustrated in Figure 14. Photodetector 1 includes a device 2 having interdigitated electrodes 3, formed therein and connected to external circuits. The external circuits comprise an excitation source 4 and a measuring instrument, such as a current meter 5. The excitation source 4 can be any suitable voltage source. In a preferred embodiment, the source is a battery that operates within the range of 5 to 25 volts. The current meter 5 can be any adequately sensitive current meter. In one mode, a model 614 of Kiethley is used. When in operation, photons (in the form of incident light) collide with the surface of the device 2. The photons of suitable wavelength are absorbed and give rise to electron-hole pairs (one for each absorbed photon) inside the device 2. The electrical conductivity of the device 2 increases in proportion to the flow of photons (photons per second). An external electric field, generated by application of the excitation voltage from source 4, causes electrons and voids to be transported within the device, thus giving rise to a current in the external circuit, which is measurable by the current meter 5. Device 2 consists of a film of an III-V nitride formed on a substrate. The III-V nitride film may consist of one or more monocrystalline layers and, preferably, is formed by molecular ray epitaxy, aided by microwave plasma resonance in electronic cyclotron (ERM assisted by RCE). Depending on the material used for the substrate, a buffer layer can be used between the substrate and the monocrystalline layer. That is, when the network is out of phase, as defined by the network constants and the crystalline structure of the substrate, and when the monocrystalline layer is large, a buffer layer can be used to form the monocrystalline layer on the substrate. When the constant network and the crystalline structure of the substrate and the monocrystalline layer are approximately equal, a layer is not necessary shock absorber As an illustration, if the III-V nitride film to be used is a GaN film and the substrate to be used is sapphire, there is an inequality or mismatch in the network of about 15%, and a buffer layer can be used to obtain the appropriate epitaxy, for example, an appropriate two dimensional growth. If, for example, SiC or ZnO were used as substrates, the inequality or mismatch of the network would only be around 3% and the buffer layer would not be necessary. According to one embodiment, the device 2 consists of three layers including a base substrate 21, a buffer layer 22 and a film 23. The base substrate 21 is a single-crystal sapphire substrate, the surface of which, after chemical cleaning and thermal degassing, is converted to A1N by exposing it to nitrogen plasma activated by resonance in electronic cyclotron (RCE). This process is called nitriding and is explained in more detail later. The buffer layer 22 is preferably deposited at a temperature between 100 ° C and 550 ° C, at a thickness of about 100 A to about 1,000 A. It is preferred to deposit the film 23 at a temperature of about 600 ° C to 900 ° C at a thickness approximate from 1,000 A to several microns. Layers 22 and 23 are preferably GaN deposited by ERM aided by RCE. Other procedures (e.g., metal-organic vapor phase epitaxy, EFVMO) could also be used to develop the films. The interdigitated electrodes 3 are arranged in design on the films, using common photolithographic and detachment techniques. Subsequently, the surface of the device 2 is coated with an anti-reflective coating. The use of the ERM procedure aided by RCE has certain advantages over other deposition procedures. The ERM procedure assisted by RCE allows the control of the resistivity of device 2, varying the parameters of the procedure, such as the power of the microwaves and the flow rate of the source of N2. This control of the resistivity of the device 2 allows the electrical properties of the photodetector to be controlled, such as the gain and the speed of response. In general, if a fast response time is desired from a photodetector, a device with greater resistance is used. The correlation between gain and resistivity is explained in more detail below. Another advantage of using ERM supported by RCE is that it produces an almost intrinsic GaN. Other procedures that can be used to deposit GaN have resulted in an n-type GaN that is unintentionally adulterated. This unintentional adulteration of the GaN has been attributed to the formation of nitrogen absences in the GaN network. The GaN decomposes (and loses nitrogen) to around 650 ° C. Many growth procedures take place at temperatures exceeding 650 ° C (for example, GaN MOCVD typically occurs at temperatures exceeding 1.0Q0 ° C) and, therefore, the growth procedure itself provides sufficient thermal energy for the formation of hollow spaces or absences . Growth procedures at lower temperatures should reduce the number of hollow sites or absences of nitrogen in the network, and prevent unintentional n-type adulteration of the GaN network, and result in an intrinsic GaN. The ERM assisted by RCE, used in the preferred embodiments of the present invention, forms GaN at significantly lower processing temperatures, using an activated nitrogen source. A microwave nitrogen plasma by RCE is the preferred activated nitrogen source. A two step heating procedure allows the formation of monocrystalline GaN at lower processing temperatures. One embodiment of an ERM system assisted by RCE, which can be used to manufacture the device 2 of the present invention, is shown in figure 1. An RCE system 10 is integrated with an ERM system 11, by joining the RCE system 10 to an effusion gate 12. The RCE 10 system can be a source of RCE AsTeX model 1000, for example. The RCE system 10 includes a microwave generator 13, a waveguide 14, a high vacuum plasma chamber 15 and two electromagnets 16 and 17. Microwaves at 2.43 GHz are created in the microwave generator 13 and move along the rectangular waveguide 14. The microwave power (100-500) passes from the waveguide 14 to the plasma chamber 15. Nitrogen flows into the plasma chamber 15 through the a mass flow controller 18. The mass flow controller 18 maintains a constant, adjustable flow rate. The plasma chamber 15 is surrounded by the two electromagnet 16 and 17. The upper magnet 16 is powered by a power supply of 2 kW (not shown) and the lower magnet 17 is powered by a 5 kW power supply ( not shown). The placement of the electromagnets in this manner results in a more intense and more stable plasma. The upper electromagnet 16 establishes free electrons in the chamber 15, in cyclotron orbits. The frequency of the cyclotron depends on the strength of the magnetic field and the charge to mass ratio of the electrons. Since all electrons assume cyclotron orbits, the energy loss in random movement and collisions is reduced. Additionally, the plasma will be confined to the center of chamber 15. The magnetic field is adjusted so that the microwave oscillation frequency is exactly equal to the cyclotron frequency of the electrons. Nitrogen (N2) is then introduced to the chamber through the mass flow controller 18 and part of it is decomposed to atomic and ionic nitrogen, and another part of it is converted to excited molecular nitrogen (N2-) by impact with the high electrons Energy. The atomic nitrogen species and the excited molecular species are known as neutral excited species. The lower electromagnet 17 then guides the ions through the melting port 12 towards a substrate 19, which is placed on, and supported by, a continuous azimuthal rotation unit 20 (RAC) in a growth chamber 21 of the ERM system 11. The growth chamber 21 is located in a housing 50, into which the effusion portholes are connected. The RAC 20 can rotate between 0 and 120 rpm-In certain substrates, the GaN films grow in the wurtzite structure and others in the zincblende structure. Such substrates include, for example, sapphire (GaN in wurtzitic structure) and Si (100) (GaN in zincblende structure). Gallium flow is generated in a nudsen effusion cell 22. In a typical procedure, it is etched by ion bombardment by the nitrogen plasma at about 600 ° C., for example. Other elevated temperatures, from about 600 ° C to about 900 ° C, for example, can also be used. This procedure performs nitriding. Nitriding is a process in which sapphire (AI2O3) is bombarded with nitrogen at relatively high temperatures. Nitrogen replaces oxygen on the surface of the sapphire and creates atomically uniform A1N. After nitriding the substrate is cooled to 270 ° C in the presence of the nitrogen plasma. A gallium plug 23 is then opened to deposit the Initial buffer layer of GaN. The use of an activated nitrogen source allows the deposition of GaN at this low temperature. The buffer layer is allowed to nucleate for ten minutes, for example, and then the gallium plug 23 is closed to stop nucleation of the film. The substrate is then brought slowly to 600 ° C at a rate of 4 * C every 15 seconds in the presence of the nitrogen plasma. Excess nitrogen pressure also helps reduce the formation of empty nitrogen sites. Once it is at 600 ° C, the substrate 19 is maintained at this temperature for 30 minutes, in the presence of nitrogen plasma to ensure that the buffer layer of GaN crystallizes. The gallium plug 23 is once again opened to develop the GaN monocrystalline film. The thickness of the film is preferably about 1 μm, although in theory there is no limit to the thickness of the film. The nitrogen pressure and the gallium flow are kept constant throughout the procedure. The two-step growth procedure allows the nucleation of a buffer layer. The buffer layer is developed at a temperature in the range of 100 ° C to 400 ° C, but an approximate scale of 100 ° C to 550 ° C can also be used. Up to about 400 ° C, the nucleation layer is mainly amorphous. Approximately 400 * C, the layer becomes crystalline with defects due to stacking faults and disoriented domains. If a amorphous nucleation layer, the layer should be relatively thin (for example, around 100-200 A), but should completely cover the substrate. In certain cases, thinner buffer layers are desirable, because the subsequent crystallization of a thin amorphous nucleation layer will be more efficient and will not take as long as with a thicker amorphous layer. An advantage of using a temperature that causes an amorphous layer is that the amorphous layers more uniformly cover the entire substrate. At higher temperatures, such as between about 400 ° C and about 550 ° C, for example, the GaN layers are crystalline, albeit slightly defective. Because the mode of development or growth at these temperatures is columnar or three-dimensional, these layers must be slightly thicker to ensure full coverage of the substrate. Crystalline, slightly defective buffer layers can be developed from about 200 A to 1,000 A, for example. After the nucleation step, the temperatures increase at a temperature level that effects a growth step. At these higher temperatures, from about 600 ° C to 900 ° C, for example, the amorphous damping layers crystallize and the crystallinity of the defective, crystalline damping layers improves. Since amorphous, thinner buffer layers crystallize at a faster rate than amorphous buffer layers more thick, it may be convenient to maintain the temperature of the chamber at a temperature higher than the nucleation temperature for a period of time before the growth or development step begins, to ensure the desired crystallization of the nucleation layer. After the amorphous buffer layer has crystallized, or that the defective crystal nucleation layer undergoes additional recrystallization, any growth takes place on the crystallized Gan buffer layer. A useful method to monitor the crystallization, the surface morphology of the buffer layer and the final film, is the High Energy Electron Diffraction by Reflection (DEAER). The films developed by this two-step procedure are superior to those developed by a one-step growth procedure. Figure 2 shows the X-ray diffraction pattern (XRD) of a GaN film developed on the sapphire alpha plane (11-20) in a one-step procedure (Figure 2A) and in a two-step procedure (Figure 2B). The two peaks at about 2"= 35 ° of Figure 2A are attributed to a defective GaN crystal. Figure 2B has a single peak indicating a better quality film. This is because most of the film is developed over the GaN buffer and does not make contact with the underlying substrate. The growth layer of GaN "recognizes" the GaN buffer layer on which it can grow without defects.

The shock absorber is the only part of the film that is highly defective. Films developed by the method described above can have great resistance to room temperature (1012 _-cm). The development procedure described above results in a GaN that is substantially intrinsic. The GaN can be adulterated with type n or with type p, incorporating the appropriate impurities, as described above. For example, silicon can be used as the n-type adulterant. Alternatively, the GaN can be self-adsorbed with empty nitrogen sites. The carrier concentration of the adulterated GaN can vary from about 1013 to about 1019 cnrr1. The adulteration is generally carried out by incorporating the appropriate impurities in their charged state. This is because the energy to incorporate an impurity with charge in the network is less than the energy necessary to incorporate a neutral impurity. Figure 3 is a schematic illustration of an apparatus for incorporating a receiver or a charged donor into the GaN network. The substrate 19 or a grid 19a, directly in front of the substrate 19, is excited positively. Figure 3 shows both the substrate 19 and the grid 19a connected to a voltage source. In the practice of this invention, either the substrate 19 or the grid 19a can be positively excited. Therefore, electrons are attracted to the surface of the substrate, while positive ions, such as N +, are repelled. He The growth process is carried out as described above, with the addition of a receiving source 24, so that gallium, nitrogen and receptors are deposited on the surface of the substrate, rich in electrons. As the receiving atom approaches the surface, it takes an electron and enters the network as a negative species. The same procedure is used to adulterate the GaN network with donor impurities, except that a negative excitation is used in the substrate or grid. Alternatively, a charged surface can be generated by bombarding the substrate with electrons or positive ions. Electronic cannons and ion cannons, respectively, are conventional sources of these species. Suitable receptor species include, but are not limited to: zinc, magnesium, beryllium and calcium. Suitable donor species include, but are not limited to: silicon, germanium, oxygen, selenium and sulfur. In another embodiment of the present invention a compact RCE source can be used to manufacture device 2 of Figure 14. Figure 4 illustrates an ERM device 100, aided by RCE, having a compact RCE system 25 mounted in a cell 30 effusion of Knudsen. Thus, this source generates a nitrogen plasma closer to the substrate 19 than a conventional RCE source. The compact RCE system 25 has an axial solenoid (not shown) to generate the magnetic field used for the operation of RCE. The compact RCE system 25 is fed with nitrogen by means of the nitrogen source 32. The nitrogen is first purified in the nitrogen purifier 28, before it enters the compact RCE system 25. The compact RCE system 25 can be a source of compact AsTeX RCE, by example. The compact RCE system 25 is preferably lightweight and relatively inexpensive, compared to traditional RCE sources, and operate at microwave powers much lower than a traditional RCE source, such as the RCE source AsTeX model 1000 , for example. The compact RCE system 25 uses a microwave power for the growth of the GaN films in the approximate range of 10-100 W. This microwave power scale leads to power densities that are approximately equal to those that are the result of operate traditional RCE sources in the approximate range of 100-500 W. In accordance with another aspect of this invention, an external solenoid may also be used. Figure 4 illustrates an ERM device 100 aided by RCE, with an external solenoid 40 attached to it. However, the ERM device 100 supported by RCE can be operated without the external solenoid 40, or it can be operated with an external solenoid 40 that has no current. In addition, the external solenoid 40 can also be used with the RCE source 10 illustrated in FIGS. 1 and 3, or with other sources of activated nitrogen. The external solenoid 40 is a magnetic device designed to induce a magnetic field. Preferably the The magnetic field induced by the solenoid 40 is of opposite sign with respect to the substrate 19, that of the magnetic field generated by the source of RCE. The external solenoid 40 may be powered with a direct current power source (not shown), for example, to induce the desired magnetic field. The external solenoid 40 may consist of a plurality of coils of copper magnet wire, wound on a mandrel. For example, 2300 turns of enameled copper magnet wire, 18 gauge, can be used on an iron mandrel. The number of turns, the type of wire and the construction of the solenoid may vary. Preferably the external solenoid 40 is fed by a current of about 5 to 8 amps. Other amperages, such as 0 to 10 amps, can also be used. As illustrated in figure 4, the external solenoid 40 is preferably disposed outside the housing of the high vacuum plasma chamber 15 of the ERM system 11. Preferably the external solenoid 40 is disposed along an axis B which is preferably arranged at an angle alpha with respect to a axis A, through the RCE system 25. In a preferred embodiment, the angle alpha is about 60 °. You can also use other values for the alpha angle. Additionally, the external solenoid 40 is preferably disposed at a reasonable distance from the magnetic winding at the source of the RCE to avoid undesirable interference at the source of RCE. In order for the source of RCE operate properly, a magnetic field of 875 gauss is used. If the external solenoid 40 is too close to the magnetic source in the RCE source, this field may be affected. When in operation, the species charged in the RCE plasmas is guided strongly along the lines of magnetic field or, in an equivalent way, following the divergence of the magnetic field, by ambipolar diffusion. Thus, the charged nitrogen species move along the compact RCE system 25, through the effusion port 12, along the magnetic field lines generated by the magnetic source of RCE to the substrate 19. external solenoid 40 alters the direction of the charged species (ionic species) that are produced from the compact RCE system 25. Additionally, due to the relatively large separation between the external solenoid 40 and the compact RCE system 25, there is a disturbance imperceptible of the magnetic field within the RCE 25 system, due to the magnetic field of the external solenoid 40. Accordingly, the effect on the species generated in the compact RCE system 25 is negligible. Figure 5 illustrates the effects of an external solenoid 40 on the direction of the charged species. Figure 5A shows the magnetic field lines produced from an RCE source, without the use of an external solenoid 40. As shown in this figure, the field lines are directed symmetrically towards the substrate 19. Figure 5B shows the magnetic field lines produced from an RCE source with an external solenoid 40 in use. The external solenoid 40 serves to deflect the field lines away from the substrate area. Therefore, by varying the power and position of the external solenoid 40, it is possible to selectively control the amount and proportion of the ions with respect to the excited neutral species and the atomic species present in the substrate. The use of the external solenoid pres a scalable procedure. By controlling the effective magnetic current of the outer solenoid 40, the ionic density in the substrate can be altered. The ionic density in the substrate can be important because the high energy ions can cause damage to the growth layer. Therefore, by reducing the amount of ions in the substrate, the probability of such damage is correspondingly reduced. Figure 6 illustrates an example of how to vary the magnetic current of the external solenoid 40 in relation to the relative ionic density. By replacing substrate 19 with the manifold of a simple ionization meter (Bayard-Alpert type) and using it as a Langmuir probe, the relative ionic density can be measured as a function of the magnetic current of the external solenoid 40. Figure 6 illustrates the possibility of scaling the development or growth procedure by means of the variation in the magnetic current of the external solenoid.

Figure 7 illustrates a characteristic IV of the Langmuir probe used, operated in the above with the external solenoid 40, having a current of 7A and without the external solenoid 40. Figure 7 illustrates the activation of the external solenoid 40, which results in the reduction in both electron and ion density at the surface of the substrate 19. The films developed with the external solenoid 40 have improved surface morphology and improved transport and photoluminescence properties. These differences are attributed to the reduced number of ions present in the nitrogen plasma. By using an external solenoid 40, films of substantially higher quality can be developed. This external solenoid thus provides a simple, effective and non-obstructive method for extracting and controlling charged species, particularly when the energetic anisotropies of the ionic species resulting from the effects of the magnetic field make it difficult to interpret the excitation schemes. In another embodiment of the present invention, damage by high energy ions can be reduced through the use of at least one small diameter outlet opening at the outlet of the RCE system. The compact RCE system 25 may be provided with exit openings 42 at its outlet, as illustrated in Figures 4 and 8. The exit openings 42 may be formed from a disc (not shown) that it has a hole or a plurality of holes disposed therein. The disc can be placed between the liner of the RCE system and a microplate spring, which holds both the liner and the disc in place. The RCE system having the disc in its outlet is then placed in the effusion port 12. The disc may be made, for example, of quartz; and it can have a thickness of approximately 1 mm. Other devices for reducing the diameter of the output of the RCE system can also be used, such as a remotely controlled shutter, for example. By using a remote control device, the operation of the exit openings 42 can be varied during operation. The material used for the construction of the RCE source and its lining can also be important to reduce the concentration and recombination of nitrogen. Materials that can be used include, for example, pyrolytic boron nitride, aluminum, tungsten, molybdenum or other metals or insulators. The outlet openings 42 preferably have a smaller diameter than the diameter of the RCE 25 dsys system, as shown in Figure 8. For example, the diameter of the RCE system, dSys can be about 2 cm, while the diameter d_? it can vary from about 1 mm to about 1.9 cm, for example, although other diameters can also be used. By reducing the diameter of the output of system 25 of RCE, the pressure inside the RCE system is increased 25. Conversely, increasing the diameter decreases the pressure. The increased pressure promotes collisions between the plasma ions. These collisions tend to reduce the energy of the ions and reduce the quantity of the ionic species leaving the CERR 25. Any ions that leave the CERR 25 system will have reduced energy and are not likely to cause damage to the growth layer of GaN . If the diameter of the outlet openings 42 is sufficiently small, no ion escapes due to a sieving effect. The diameter at which "sieving" occurs is known as the Debye sieving length. However, atomic nitrogen particles pass through this "screen". The atomic nitrogen species is preferred to form the GaN layers. Controlling the diameter of the exit openings 42 controls the amount of the ionic species and the ionic energy in the substrate. A smaller hole allows fewer ions and ions to pass with reduced energy. In some applications, it may be desirable to provide more than one opening 42 at the outlet of the RCE 25 system. By controlling the diameter of the openings used (e.g., maintaining diameters less than the length of Debye), the pressure within the system and high-energy ion damage is reduced. However, the use of multiple apertures does not unduly restrict the flow of N2 within the growth chamber 21. The exit aperture 42 can also beused with or without external solenoid 40. Exit aperture 42 can also be used with any suitable type of RCE system or other source of activated nitrogen, to vary the ionic energy directed to the substrate. By using both the outlet openings 42 and the external solenoid 40, greater flexibility can be provided by controlling the development or growth procedure. Figures 9 and 10 illustrate the effects of using the outlet openings 42. Figure 9 illustrates an optical emission spectrum for a nitrogen plasma of RCE, generated by a compact RCE system, operated at 35 W, with a pressure of nitrogen of about 1.2 x 10 ~ * torr, without the use of an exit opening. This figure illustrates the presence of ionic nitrogen (N2 +) at around 391.4 nm, excited molecular nitrogen (N2 *) and atomic nitrogen (N). The energy of atomic nitrogen (N), which occurs at wavelengths of more than about 650 n, is relatively small. Figure 10 illustrates an optical emission spectrum for a nitrogen plasma of RCE generated by a compact RCE system having an outlet opening 42 with a diameter of 1 mm, operated at around 30 W. Figure 10 illustrates peaks pronounced atomic nitrogen at approximately 625 nm and 670 nm. Additionally the peak at around 391.4 nm for the ionic nitrogen is reduced with respect to the size of the atomic nitrogen peaks. As those figures indicate, the proportion of energy ionic species to atomic species it is reduced by the use of the exit aperture 42. While these figures illustrate the results of ERC systems operated at different power levels, the RCE system operating with an exit opening at 35 W would create even larger amounts of atomic nitrogen . Therefore, these figures show the increase in atomic nitrogen output, which is created by increasing the pressure in the RCE system through the use of an exit opening. The reduced amount of ionic species reaching the substrate, with the use of the outlet opening 42 having small holes, allows the source of RCE to be operated at high powers (up to 500 W). This operation at high power leads to more atomic nitrogen. The effects of using the outlet openings 42 are also illustrated in Figure 11. Figure 11 illustrates the ratio of ionic to excited nitrogen species, taken for various sizes of the exit openings 42 and variable nitrogen flow rates. The tables represent a reading of an RCE source that operates without an exit opening. The circles represent readings for an RCE source that operates with an output aperture of 1 cm. The triangles represent readings for an RCE source that operates with an output aperture of 1 mm. As illustrated in Figure 11, when the diameter of the outlet opening 42 is smaller, the relative ion emission intensity is lower, even for different nitrogen flow rates.

The use of the external solenoid and / or the use of the restrictive outlet openings in the RCE system allows the adulteration of the non-type p type in the GaN, without the use of excitation of the substrate, as discussed with reference to the figure 3. Adulteration with an outer magnet or with a small diameter outlet opening can be achieved by directing a current of gallium, activated nitrogen and the appropriate adulterant, to the substrate. A more detailed explanation of device 2 is now presented, which incorporates details of the ERM method assisted by RCE. Figure 12 illustrates the device 2 in section and includes the substrate 100, the buffer layer 102, the monocrystalline layer 104, the electrodes 106 and the anti-reflective coating 108. Initially, the substrate 100 is placed in the ERM system. If the substrate is sapphire, then sapphire is preferably subjected to nitriding, at a temperature of the order of 850 ° C, for example, to form atomically uniform A1N. Other methods for preparing the substrate for GaN growth can also be used. The preparation depends on the substrate used. Once the substrate is prepared, the temperature in the ERM chamber is set at between about 100 ° C and about 550 ° C to effect a nucleation step to develop a buffer layer of the desired thickness. In a device 2 embodiment, the buffer layer is developed 102 of GaN at a temperature of about 550 ° C to a thickness of about 400 A. As described above, temperature is a factor in determining whether the nucleation layer will be amorphous or crystalline defective. At that temperature, the activated nitrogen from an RCE system and the atomic gallium generated by the Knudsen effusion cell 22 are directed to the substrate 100. Other temperatures and other thicknesses can be used. Preferably, the compact RCE system 25 is used to generate the activated nitrogen. The microwave power of the compact RCE system 25 affects the type of development that is induced. Figure 13 illustrates the effect of microwave energy on the surface morphology of the films. At an enlargement of 25,000 times, Figure 13 (a) illustrates the surface of a film developed at 18 W; Figure 13 (b) illustrates the surface of a developed film at 20 W and Figure 13 (c) illustrates the surface of a developed film at 25. At 18 W, the film has a development structure relatively similar to an island. The film developed at 20 W shows a relatively smooth surface, typical for layer by layer development. The film developed at 25 W shows a three-dimensional development that leads to rugged surface morphologies. An energy of about 20 W is preferred to provide a uniform development layer by layer, as illustrated in Figure 13 (b). However, other energies may be used, depending on the desired parameters. For example, when an outlet opening is used in the RCE system and / or the external solenoid, the optimum energy in the compact RCE system 25 is between about 30 and 500 watts, and preferably between 25-250 watts. After the buffer layer 102 is grown, the substrate 100 is gradually heated to a rate of approximately 4 ° C every fifteen seconds. Other regimes may also be used to increase the temperature, depending on the initial quality of the nucleation layer. For example, if the nucleation layer is amorphous, a slower rate of temperature rise can be used to ensure that the buffer layer crystallizes. The substrate is heated to the desired elevated temperature, to effect one or more growth steps. A temperature on the scale of about 600 ° C to 900 ° C, such as about 800 ° C, can be used, for example, during the growth steps. Before proceeding to the growth or development step, it is important to determine if the buffer layer has begun to crystallize. A high energy reflection diffraction electron (DEAER) apparatus 46 (Figures 1, 3 and 4) can be used to monitor the crystallinity of the nucleation layer. For amorphous materials, it may be convenient to maintain the temperature at a predetermined elevated temperature for a predetermined period of time, such as at 800 ° C, for about 30 minutes, for example, before opening the Gallium shutter to start the growth step. When the desired temperature is established and the crystallinity of the nucleation layer has reached a desired level, the gallium plug 23 is opened to begin the growth of a monocrystalline layer 104 on the buffer layer 102. In one embodiment of device 2, the monocrystalline layer 104 is a n-type layer, preferably developed to a thickness of about 1.0 to 3.0 μm, at a deposition rate of about 0.2 μm / hour, for example. In a preferred embodiment of device 2, shown in figures 12 and 14, the n-type layer was developed at a temperature of about 800 ° C, up to a thickness of approximately 2 μm. As described above, the development of the n-type GaN can occur by self-adsorption or by introduction of a donor impurity. A level of adulteration of between 1013 and 1019 cpr3 of net carrier concentration can be used. Once layer 104 has been developed to the desired thickness, electrodes 106 are formed using standard photolithographic and survey techniques. To obtain optimum performance of the device, it is preferred to obtain stable ohmic contacts of low resistance. The Al is a suitable material for the formation of ohmic contacts in GaN. However, there is a limitation to the use of pure Al. That is, the Al can be diffused into the semiconductor during the annealing, an important process to obtain the low contact resistivity. Therefore, it is preferable to use a combination of. Ti and Al to form interdigitated electrodes 106. For example, electrodes 106 can be formed by depositing a thin layer of Ti (approximately 200 angstroms) on the surface of device 2, followed by an Al layer (approximately 2,000 angstroms) . These layers can be deposited at room temperature by evaporation with electronic beam. After depositing, the device is subjected to rapid thermal recovery (RTR) for 30 seconds at a temperature between about 700 ° C and about 900 ° C, which results in a reduction in contact resistance of approximately three orders of magnitude. These contacts remain stable and ohmic for temperatures up to around 250 ° C. The interdigitated electrodes 106 can be manufactured with a finger width W of between about 1 micrometer to about 100 micrometers and a spacing between electrodes, S, of between about 1 micrometer and about 100 micrometers. The total surface area of the device can vary and, preferably, is between about 0.5 and about 1 square mm. In one embodiment, the surface area of the device was 0.5 mm2 and the finger width and electrode spacing were both around 20 microns. After the formation of the electrode, the surface of the device 2 is covered with an anti-reflective coating 108. The GaN ordinarily reflects a substantial amount of light, that is, around 20%. By incorporating the anti-reflective coating 108 onto the surface of the device 2, the amount of light absorbed by the photodetector is increased. Therefore, the photon flux is increased. Suitable anti-reflective coatings will have a refractive index approximately equal to the root of the product of the refractive indices of film 104 in device 2, and the surrounding atmosphere. For a surrounding atmosphere of air, the coating should have a refractive index approximately equal to the square root of 3. The SIO2 and the SiN are examples of materials that can be used as anti-reflective coatings. The anti-reflective coating is preferably applied so that its thickness is equal to about one quarter of the wavelength of operation. For example, if the device 2 is to be used in a photodetector to detect light having wavelengths on the ultraviolet scale (around 200-400 nm), the anti-reflective coating will preferably be applied with an approximate thickness of 75. nm (one quarter of 300 nm). The anti-reflective coating can be deposited by means of ERM assisted by RCE, M0CVD, sputtering or any other suitable process. The gain of the photodetector of Figure 14 is realized because the recombination life and the time of transit generally differ. Suppose that the holes are trapped in states due to defects and impurities and, in such a way, the electron-hole recombination life is very long. In that scenario, an electron will move through the circuit many times, before recombination. Therefore, the absorption of a single photon results in an electron passing many times through the external circuit. The expected number of electron trips constitutes the gain, G, and can be calculated as the recombination life, ", divided by the transit time of the carrier, tr: The transit time depends on the physical dimensions of the device and can be calculated as the path length (L (electrode spacing) divided by the travel speed of the carrier, _d: The speed of displacement depends on the strength of the electric field through the semiconductor, E (which depends on the magnitude of the excitation voltage, V) and the mobility of the carrier, μ: Vd = μE = μV / L (3) The photocurrent in the circuit of figure 14 is expressed then by the following relation: IPh = nqAIo (lR) (le »«) G (4) where: n = quantum efficiency q = electronic charge A = detector area lo = intensity of incident light R = material reflectivity a = material absorption constant d = thickness. As mentioned before, an advantage of using the ERM process aided by RCE is that the gain of the photodetector can be controlled by adjusting the parameters of the ERM process aided by RCE. For example, the resistivity of the GaN can be varied by varying the microwave energy. The resistivity of five GaN samples is plotted against the microwave energy in Figure 15. Figure 15 shows that as the microwave energy used in the ERM process aided by RCE increases, the resistivity of the sample also increases. This control of the resistivity of the sample allows the gain of the photodetector to be controlled. This is so because the life of recombination, ", depends on the resistance of the device. The gain of a photodetector can be determined from equation (4), since all the other quantities in That equation is either constant or easily measurable. In addition, by substituting equations (2) and (3) in equation (1), the gain can be expressed as follows: G = (μt) V / L2 (5) The gain is influenced by the internal parameter, ie, (μt), as well as by the photodetector circuit parameters, ie, V / L2. Several samples were tested and the results indicate that as the resistivity of the sample increased (adjusting the deposition parameters), the product of mobility and recombination life (which can be determined from equation (5)) decreased. ). Mobility is generally believed to be constant. Therefore, a decrease in the life of recombination causes the decrease in (μt). A graph of the results of the test, which shows that (μt) depends on the resistivity of the sample, is shown in Figure 16. By appropriate control of the resistance of the sample, the photodetectors according to the preferred embodiments can achieve gains of up to 5,000. The resistivity of the sample can also be controlled by varying the flow rate of 2 in the ERM procedure aided by RCE. That is, when the flow rate of 2 decreases, the resistivity of the sample increases. The flow rate variation of N2 could be used as an alternative to, or in conjunction with, the variation in microwave energy. Accordingly, by varying the parameters of the ERM procedure aided by RCE, in accordance with the data shown in Figures 15 and 16, the GaN can be given a predetermined resistivity. That predetermined resistivity, in turn, allows the gain and response time of the photodetector to be predetermined, by using the relations (l) - (5). The nature of blindness to visible light, of a photodetector, is evidenced by its spectral response. The spectral response of a photodetector is determined by the frequency, which depends on its photo-response. Photo-response is a function of wavelength, mainly because the absorption coefficient is a function of wavelength. For photons with energy lower than the band gap energy of the semiconductor, the photon energy is insufficient to excite the carriers to overcome the band gap and, thus, no absorption occurs. Thus, the limit of the long wavelength of the spectral response is set by the band gap of the material. For photons with energy greater than that of the band gap, an excess of photocarriers is created proportional to the incident excitation. In most semiconductors, for very short wavelengths, the photoresponse decreases because most of the photons are absorbed close to the surface of the device, where the recombination life is short. Figure 17 illustrates the spectral response of photodetector 1. The spectral response was measured using a UV-visible spectrometer which used a xenon lamp as a source of UV light and a tungsten lamp as a source of visible light. The photo-response was calculated from the photocurrent measurement produced by the GaN detector as a function of the wavelength and was normalized to that produced by a silicon photodiode, with increased UV, calibrated, of equal active area. As can be seen from Figure 17, the spectral response of the photodetector 1 remains constant for wavelengths between about 200 nm and about 365 nm, when the photoresponse drops abruptly. The transition wavelength of 365 nm corresponds to the band gap energy of the GaN. The response shown in Figure 17 indicates the nature of blindness to the visible light of the GaN detector. Additionally, said spectral response indicates that no surface states or surface recombination are present in the GaN. The spectral response shown in Figure 17 was obtained through the use of GaN alone. In other embodiments, a photodetector using a GaN alloy and InN or A1N alloy may be used instead of Gan alone. The use of an InN and GaN alloy results in a spectral response in the same general way as that shown in Figure 17, but with the transition wavelength shifted to the right (ie, in the direction of the increasing wavelength). The use of this type of alloy allows things such as blue-violet detectors. Additionally, by varying the amount of InN in the alloy, the transition wavelength can be fully shifted to around 600 nm (which corresponds to the pure InN and a band gap of about 1.9 eV). In contrast, by using an A1N and GaN alloy, the transition wavelength can be shifted to the left (ie, in the direction of the decreasing wavelength). When the amount of A1N in the alloy is increased, the transition wavelength can be decreased to about 200 nm (corresponding to pure A1N and a band gap of about 6.2 eV). In this way, the photodetector can become completely blind to sunlight, by shifting the transition wavelength to around 270 nm. The introduction of Al and In in GaN can be achieved by evaporating those elements from special effusion cells in the ERM chamber. In another photodetector embodiment, GaN with p-type adulteration can be used to form device 2. The operation of photodetectors that have p-type adulteration is similar to the operation of photodetectors that have n-type adulteration. However, the formation of the contacts is slightly different. To form an ohmic contact, the metal used generally has a work function approximately equal to the semiconductor work function (GaN, in this case). The work function of the adulteration of GaN with type p, is of the order of 7.5 eV. Platinum has the maximum known work function, of any metal, at around 5.8 eV. Accordingly, an electron channeling method for contact formation is generally used to approximate an ohmic contact in a p-type semiconductor. To form an electron channeling contact, a higher carrier concentration (of the order of 1019 to 1020 cpr3) is used in the vicinity of the contacts, to facilitate the channeling of electrons. In another photodetector embodiment, the three layers 21, 22 and 23 of the device 2 shown in Figure 14 can be replaced by a single n-type GaN substrate, or by a GaN substrate having a GaN layer epitaxially formed on him. An example of a method by which a n-type GaN substrate can be provided is explained in conjunction with Figure 18. Figure 18 illustrates a developmental structure by which a gallium nitride semiconductor can be produced. Beginning with a substrate 70, an intermediate layer 71 is developed which dissolves, by sputtering or by ERM aided by RCE. The substrate 70 may be sapphire, for example; but it also You can use other substrates. The dissolving intermediate layer 71 can be ZnO or SiC, for example, but other intermediate layers that dissolve can also be used. If SiC is used, SiC can be developed on the sapphire substrate using a silicon-on-sapphire growth method. Si is converted to SiC by methane exposure, at a temperature of about 800 ° C to 1,000 ° C, for example. A n-type GaN substrate 72 is then epitaxially developed over ZnO or SiC by the chloride transport method, for example. The chloride method is given by the following equations: 2Ga + 2HC1 - > 2GaCl + H2 GaCl + NH3 - > GaN + HCl + H2 The chloride transport method is generally operated at elevated temperatures of about 1050 ° C to 1200 ° C. Approximately at 100 ° C, Ga-N ligatures are broken from the GaN layer that is forming on the ZnO or SiC layer. Therefore, empty nitrogen sites are created that make the GaN substrate self-adhered, type n. Intentional tampering can also be used, by adding Si to the procedure, for example. Preferably, the n-type GaN substrate 72 is adulterated at a carrier concentration level of about 1020 cpr3, for example. You can also use a Carrier concentration of about 1019 cm-3. Higher carrier concentrations can also be used. Substrate 72 of GaN of type n is preferably developed to a thickness of approximately 0.5 mm, to give a suitable substrate. The chloride transport method is advantageous because development rates of about 0.5 mm / hour can be obtained. Therefore, a GaN substrate can be developed in about one hour. Other methods can also be performed to develop a GaN layer. For example, a GaN substrate can be provided by high pressure, high temperature formation by reaction of liquid Ga with ammonia. After the development of GaN is completed, the substrate 72 is removed by removing the layer 71 that can be dissolved, using an appropriate acid or base solution. Once separated, the GaN substrate 72 is used to form the device 2 shown in Figure 14. In one embodiment an epitaxial GaN layer is formed on the substrate 72 and the interdigitated electrodes 3 are formed thereon. The epitaxial layer can be formed using the ERM method aided by RCE, described above, and can be of type n or p type. Alternatively, the substrate 72 can be used without forming an additional epitaxial layer thereon. In this case, the interdigitated electrodes 3 are formed directly on the substrate 72. In another embodiment, two detectors can be used. independent together to form a bandpass detector. The photoresponse of said detector is shown in Figure 19. Briefly, two detectors are fabricated having the lower and upper transition wavelengths (annotated A and B, respectively). For example, this can be done by forming GaN alloy with InN and with A1N. The two detectors can be independently developed on separate substrates, trimmed and then mounted on a single substrate. Alternatively, the two detectors can be developed on the same substrate using the ERM method aided by RCE, and the appropriate masking technology. As will be apparent to those skilled in the art, the photoresponse of the detectors can be adjusted, so that the intensity of the incident light within a particular narrow wavelength scale, the spectral region A-B, can be determined. The response of the spectral region A-B is obtained by subtracting the outputs of the two independent detectors, whose maximum photo responses were adjusted to be equal. This could be achieved by modifying the parameters of the ERM procedure aided by RCE and / or by using external circuits. In another embodiment, the photodetectors described above can also be used to detect low energy X-rays. As an example, we used an X-ray tube capable of providing X-ray photons with energies that couldset from around 50 KVp to around 90 KVp, as an X-ray source to irradiate the GaN photodetector. The outlet of the tube was filtered by means of an aluminum filter. The GaN photodetector was irradiated with X-rays and the photo-current generated in the detector was recorded as a function of the excitation voltage. Figure 20 shows the response of the GaN photodetector to the X-ray photons as a function of the X-ray photonic energy, at an excitation voltage of 100 V. As can be seen from figure 20, the response of the photodetector of GaN is linear. In yet another embodiment, the photodetectors described above could be used as alpha particle detectors. As an illustration of this, the GaN photodetector, whose response is described in Figure 17, was also used to detect alpha particles. More specifically, in the experiment carried out, a source of alpha particles having energy of about 5.5 MeV was used. Because the thickness of the detector was considerably less than the scale of the alpha particles, the detector was tilted at an angle of 45 ° with respect to the alpha particle source. This configuration increased the amount of energy deposited in the GaN layer, increasing the effective thickness of the detector, whose actual thickness was around 2 microns. For an ideal detector of alpha particles, the thickness of the detector should be increased to around 100 microns. The results of this experiment indicate that the detectors could be used GaN as single-particle radiation detectors. While the invention has been described with reference to the specific embodiments, the invention is not intended to be limited thereto. The invention is limited only by the claims that follow.

Claims (22)

NOVELTY OF THE INVENTION CLAIMS

1. - A detector characterized in that it comprises at least one monocrystalline III-V nitride film, deposited by molecular beam epitaxy, aided by microwave plasma in electronic cyclotron resonance; wherein the product (μt) of the detector is controlled by varying the parameters of the deposition process for the monocrystalline film.

2. The detector according to claim 1, further characterized in that it is a UV radiation detector.

3. The detector according to claim 1, further characterized in that it is an X-ray detector.

4. The detector according to the claim 1, further characterized in that it is an alpha particle detector.

5. A photodetector, characterized in that it comprises: a nitride film of III-V, having a predetermined product (μt); a first electrode, deposited on a surface of the film; a second electrode, deposited on the surface of the film; the second electrode of the first electrode being spaced; and a voltage source connected through the first and second electrodes; creating the voltage source an electric field within the film; where, when the surface of the film on which electrodes are deposited, subjected to photonic illumination, electron-hole pairs are created and flow into the film due to the electric field.

6. The photodetector according to claim 5, further characterized in that the III-V nitride film includes a buffer layer and a monocrystalline film.

7. The photodetector according to claim 6, further characterized in that the buffer layer is deposited on a sapphire substrate and the monocrystalline film is deposited on the buffer layer, so that the product (μt) of the photodetector is controlled by varying the parameters of the deposition procedure.

8. The photodetector according to claim 7, further characterized in that the method of deposition is an epitaxy with molecular beam, aided by microwave plasma, resonance in electronic cyclotron.

9. The photodetector according to claim 8, further characterized in that the resistivity of the film is controlled by varying the microwave energy used in the molecular beam epitaxy process, aided by microwave plasma, of electron cyclotron resonance.

10. The photodetector according to claim 8, further characterized in that the resistivity of the film is controlled by varying the flow of nitrogen used in the process. the molecular beam epitaxy procedure aided by microwave plasma resonance in electronic cyclotron.

11. The photodetector according to claim 5, further characterized in that the first and second electrodes are deposited so as to form ohmic contacts on the surface of the film.

12. The photodetector according to claim 5, further characterized in that the nitride film of III-V is manufactured from GaN.

13. The photodetector according to claim 5, further characterized in that the nitride film of III-V is manufactured from an alloy of GaN and A1N:

14. The photodetector according to claim 5, further characterized in that the III-V nitride film is manufactured from a GaN and InN alloy.

15. A method for forming a photodetector having a predetermined product (μt), characterized in that it comprises the steps of: manufacturing a III-V nitride film so as to control its resistivity; depositing a first electrode on a surface of the film; deposit a second electrode on the surface of the film; the second electrode of the first electrode being spaced; and providing a voltage source connected through the first and second electrodes.

16. The method according to the claim 15, further characterized by the manufacturing step further comprises making the III-V nitride film on a substrate. 17.- The method according to the claim 15, further characterized in that the manufacturing step further comprises making a buffer layer on a substrate and making a monocrystalline film on the buffer layer. 18. The method according to claim 15, further characterized in that the manufacturing step further comprises making a dissolvable layer on the substrate; and making a monocrystalline III-V nitride film on the dissolvable layer. 19. The method according to claim 18, further characterized in that the manufacturing step further comprises separating the monocrystalline III-V nitride film from the dissolvable layer. 20. The method according to claim 15, further characterized in that the manufacturing step comprises molecular beam epitaxy aided by resonance plasma in electronic cyclotron. 21. The method of compliance with the claim 15, further characterized in that the product (μt) is controlled by varying the parameters of the manufacturing step. 22. The method according to the claim 21, further characterized because the manufacturing step It comprises molecular beam epitaxy aided by plasma resonance in an electronic cyclotron. 23- The method according to the claim 22, further characterized in that the product (μt) of the photodetector is controlled by varying the microwave energy used in the molecular beam epitaxy procedure aided by resonance plasma in electronic cyclotron. 24.- The method of compliance with the claim 22, further characterized in that the product (μt) of the photodetector is controlled by varying the flow of nitrogen used in the molecular beam epitaxy procedure aided by resonance plasma in electronic cyclotron. 25. The method according to claim 15, further characterized in that the first and second electrodes are deposited so as to form ohmic contacts. 26. The method according to claim 15, further characterized in that the manufacturing step further comprises making the III-V nitride film from GaN. 27.- The method of compliance with the claim 15, further characterized in that the manufacturing step further comprises making the III-V nitride film from an alloy of GaN and A1N. 28.- The method according to claim 15, further characterized in that the manufacturing step further comprises manufacturing the nitride film of III-V from an alloy of GaN and InN. 29.- A bandpass photodetector for detecting electromagnetic radiation having a wavelength between a lower transition wavelength and a longer wavelength, the photodetector comprising: a first photodetector that has a maximum response for lengths wave below the lower transition wavelength; a second photodetector having a maximum response signal equal to the maximum response of the first photodetector for wavelengths below the upper wavelength; so the response of the bandpass photodetector is generated by subtracting the responses of the first photodetector and the second photodetector. 30. The bandpass photodetector according to claim 29, further characterized in that the first photodetector further comprises a photodetector manufactured from GaN. 31.- The bandpass photodetector according to claim 29, further characterized in that the first photodetector further comprises a photodetector manufactured from an alloy of GaN and AIN. 32. The bandpass photodetector according to claim 29, further characterized in that the first photodetector further comprises a photodetector manufactured from an alloy of GaN and InN. 33.- The bandpass photodetector of conformity with claim 29, further characterized in that the second photodetector further comprises a photodetector manufactured from GaN. 34.- The bandpass photodetector according to claim 29, further characterized in that the second photodetector further comprises a photodetector manufactured from an alloy of GaN and AIN. 35.- The bandpass photodetector according to claim 29, further characterized in that the second photodetector further comprises a photodetector manufactured from an alloy of GaN and InN.