Laser active region and high power long wave quantum cascade laser

Abstract

The present invention discloses a laser active region and a high-power long-wave quantum cascade laser. The laser active region includes a light-emitting layer and an injection layer, and the light-emitting layer and the injection layer respectively have a quantum well structure in which a quantum well layer and a quantum barrier layer are alternately stacked; the emission wavelength of the light-emitting layer is 8μm-12μm, and satisfies the emission of oblique transitions; the light-emitting layer includes a first quantum barrier layer, a first quantum well layer, a second quantum barrier layer, a second quantum well layer, a third quantum barrier layer and a third quantum well layer arranged in sequence; among all the quantum barrier layers of the light-emitting layer, the first quantum barrier layer is the thickest; the first quantum well layer includes two Ga component materials, and the Ga component ratio in each Ga component material is 38%-47%; the second quantum barrier layer includes two Al component materials, and the Al component ratio of each Al component material is 55%-68%. The present disclosure can improve the band shift, suppress the leakage of carriers from the upper laser state, and improve the WPE of the long-wave infrared quantum cascade laser.

Description

Technical Field

[0001] The invention relates to the field of semiconductor laser physics and device technology, and in particular to a laser active region and a high-power long-wave quantum cascade laser. Background Art

[0002] With the development of high-power quantum cascade lasers, there has been a recent surge of interest and research in the long-wave infrared (LWIR, λ = 8-12μm) region of the spectrum. This is due to the abundance of molecular species with their absorption characteristics in this range and reduced water absorption. These properties allow long-range atmospheric transmission of infrared light for a range of applications including chemical and biological sensing, infrared spectroscopy, infrared countermeasures, and free-space communications. Quantum cascade lasers (QCLs) are currently the most ideal single-pole quantum devices to realize these applications.

[0003] Long-wave infrared quantum cascade lasers have attracted much attention due to their wavelength matching the atmospheric window and molecular fingerprint absorption bands. This has led to their widespread application in a variety of fields, including chemical and biological sensing, infrared spectroscopy, infrared countermeasures, and free-space communications. Although LWIR-QCLs have achieved continuous wave operation at room temperature as early as 2002, the development of high-power long-wave infrared lasers has lagged behind due to technical difficulties such as short upper-level carrier lifetime, increased non-radiative leakage in the injection region, low voltage efficiency, and high waveguide losses in LWIR-QCLs. In recent years, LWIR-QCLs have again attracted widespread attention due to their huge commercial value and numerous related research results. Long-wave infrared QCLs grown by molecular beam epitaxy have always dominated in terms of laser performance, because the MBE high vacuum technology can accurately control the layer thickness, resulting in sharp interfaces. However, due to the low capacity and high cost of MBE, it is difficult to meet industrial needs. Therefore, metal organic chemical vapor deposition, which has the characteristics of large capacity, high efficiency and low cost, has become a competitive choice for III-V semiconductor manufacturing in industrial environments. With the development of MOCVD technology, the material quality of the heterojunction interface grown by MOCVD is comparable to that of the material grown by MBE. Many research teams have conducted research on MOCVD-grown long-wave infrared QCLs and have achieved remarkable success. However, few teams have been able to simultaneously achieve high-power and high-characteristic-temperature light sources under extreme environments. Although Fujita et al. reported that the 8.7μm emitting QCL designed with DAU can obtain a fairly high characteristic temperature, the power of the device in CW mode at room temperature is only below 400mW. In addition, although M. Troccoli and F. Xie used MOCVD to grow QCLs with relatively high CW output power at 8.9μm and 10μm, respectively, the performance of their lasers decreased significantly at high temperatures, which is not conducive to the application of lasers. Botez et al. designed a multi-component active region structure and achieved 8μm QCLs with high pulse power and high characteristic temperature, but the design of the multi-component active region in their lasers may be more complicated and not conducive to industrial production. Summary of the invention

[0004] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a laser active region and a high-power long-wave quantum cascade laser, which can improve the injection efficiency of upper laser energy level carriers, improve the extraction efficiency of carriers, and prevent thermal backfill of lower carriers.

[0005] The present disclosure provides a laser active region, comprising a light-emitting layer and an injection layer, wherein the light-emitting layer and the injection layer respectively have a quantum well structure in which quantum potential well layers and quantum potential barrier layers are alternately stacked; the emission wavelength of the light-emitting layer is 8 μm-12 μm, and satisfies the emission of oblique transition;

[0006] The light-emitting layer includes a first quantum barrier layer, a first quantum well layer, a second quantum barrier layer, a second quantum well layer, a third quantum barrier layer and a third quantum well layer which are arranged in sequence; among all the quantum barrier layers of the light-emitting layer, the first quantum barrier layer is the thickest; the first quantum well layer contains two Ga component materials, and the Ga component ratio of each Ga component material is 38%-47%; the second quantum barrier layer contains two Al component materials, and the Al component ratio of each Al component material is 55%-68%.

[0007] The present disclosure can improve the band shift so that the band shift is sufficient to fully utilize the smaller transition energy of the long-wave infrared quantum cascade laser, suppress the leakage of carriers from the upper laser state, and thus improve the WPE of the long-wave infrared quantum cascade laser. The first quantum barrier layer in the light-emitting layer is the thickest quantum barrier layer in the entire light-emitting layer. This structure can adjust the transition efficiency of the carriers, can efficiently transport the carriers, reduce the loss of excess hot carriers, and at the same time improve the internal quantum efficiency as much as possible; improve the number of carriers in the upper and lower energy levels of the light-emitting layer in the active region, and obtain a good particle number inversion effect. The first quantum potential well layer contains two Ga component materials, and the ratio of Ga in the two Ga component materials is adjusted according to the required wavelength and the stress of the overall material, so as to realize the transition of a part of the carriers, and provide a part of the design for the multi-path channel of the lower energy level, and at the same time provide a degree of freedom for the band extension.

[0008] Optionally, in the first quantum well layer, the Ga component ratio in the Ga component material close to the first quantum barrier layer is 47%, and the Ga component ratio in the Ga component material close to the second quantum barrier layer is 38%-46%.

[0009] Optionally, in the second quantum barrier layer, an AIAs intercalation layer is provided between the two Al component materials of the second quantum barrier layer. The introduction of the AIAs intercalation layer can increase the energy interval between the parasitic energy level and the upper energy level, thereby reducing the probability of carriers escaping to the parasitic energy level and improving the injection efficiency; it is beneficial to improve the temperature characteristics of the quantum cascade laser, increase the operating temperature of the device, and is more promising in extreme working environments.

[0010] Optionally, the second quantum well layer contains a component material with strained InGaAs. It can prevent thermal backfill of lower-layer carriers, effectively improve voltage efficiency, promote the improvement of WPE of QCL, and promote rapid transfer of carriers. At the same time, the flexibility of structural design is improved. In this design, the transition occurs between state 4 and state 3 to the mini-band, so that the multi-transition channel leads to a wide gain spectrum. The third quantum barrier layer contains strained InAlAs, which meets the Bragg reflection condition. The third quantum well layer contains two components of InGaAs, which can adjust the transport channel of carriers at the lower energy level, realize multi-channel carrier channels as much as possible, and improve the design flexibility for overall strain compensation.

[0011] Optionally, the injection layer is designed based on maximizing the difference η3τ3-η2τ2 and minimizing the ratio τ2 / τ32, where η3 represents the injection energy level E inj The injection efficiency to the next energy level E3, η3 represents the injection energy level E inj The injection efficiency to the next energy level E2, τ3 refers to the lifetime of E3 carriers, τ32 represents the lifetime of carriers on E3 transitioning to E2, and τ2 refers to the lifetime of E2 carriers.

[0012] Optionally, the injection layer has a thickness of 2.0 nm-4.0 nm.

[0013] Optionally, the two Ga component materials contained in the first quantum well layer are In0.56Ga0.44As and In0.53Ga0.47As.

[0014] Optionally, the second quantum barrier layer contains two Al component materials, namely In0.33Al0.67As and In0.52Al0.48As.

[0015] Optionally, the tensile strain and compressive strain of the active region are equal; the injection layer satisfies kw / Hw+kb / Hb=π, kw is the wave vector of the wave function in the quantum potential well layer of the injection layer, kb is the wave vector of the wave function in the quantum potential barrier layer of the injection layer, Hw is the width of the quantum potential well layer of the injection layer, and Hb is the width of the quantum barrier layer of the injection layer.

[0016] The present disclosure also provides a high-power long-wave quantum cascade laser, comprising an upper waveguide layer, a lower waveguide layer, and an active region disposed between the upper waveguide layer and the lower waveguide layer, wherein the active region comprises at least one of the above-mentioned laser active regions.

[0017] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The disclosure of the present invention will become more easily understood with reference to the accompanying drawings. It is easy for those skilled in the art to understand that these drawings are only for illustrative purposes and are not intended to limit the scope of protection of the present invention. In addition, similar numbers in the figures are used to represent similar components, among which:

[0019] Figure 1 It is a schematic structural diagram of a laser active region provided in an embodiment of the present disclosure.

[0020] Figure 2 It is a specific example of the structure of the growth of long-wave (9-10μm) quantum cascade laser and the structure of the active region.

[0021] Figure 3 It is a high-resolution XRD2Theta-Omega diagram of a specific example long-wave (9-10μm) quantum cascade laser sample material.

[0022] Figure 4 This is a high-resolution atomic force microscope image of a specific example long-wave (9-10μm) quantum cascade laser sample material.

[0023] Figure 5 It is the PIV curve of the pulse peak of a specific long-wave (9-10μm) quantum cascade laser sample.

[0024] Figure 6 It is the room temperature electroluminescence spectrum of a specific long-wave (9-10μm) quantum cascade laser sample.

[0025] In the figure:

[0026] 100 light emitting layer, 101 first quantum barrier layer, 102 first quantum well layer, 103 second quantum barrier layer, 104 second quantum well layer, 105 third quantum barrier layer, 106 third quantum well layer, 1031 AIAs intercalation layer,

[0027] 200 is an injection layer, and 201 is a terminal quantum well layer. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0031] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, or the positions or positional relationships in which the invention workpiece is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0032] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "disposed" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0034] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0035] The embodiment of the present disclosure provides a laser active region structure, the active region includes a light-emitting layer 100 and an injection layer 200, the light-emitting layer 100 and the injection layer 200 respectively have a quantum well structure in which quantum well layers and quantum barrier layers are alternately stacked; the emission wavelength of the light-emitting layer 100 is 8μm-12μm, and satisfies the emission of oblique transition. The tensile strain and compressive strain of the active region are equal. The injection layer 200 satisfies kw / Hw+kb / Hb=π, kw is the wave vector of the wave function in the quantum well layer of the injection layer 200, kb is the wave vector of the wave function in the quantum barrier layer of the injection layer 200, Hw is the width of the quantum well layer of the injection layer 200, and Hb is the width of the quantum barrier layer of the injection layer 200. The thickness of all quantum well layers in the active region is between 2.7nm and 6.0nm, and the average width of the quantum well layer is between 3.0nm and 4.0nm.

[0036] See also Figure 1 The light emitting layer 100 includes a first quantum barrier layer 101, a first quantum well layer 102, a second quantum barrier layer 103, a second quantum well layer 104, a third quantum barrier layer 105 and a third quantum well layer 106 which are arranged in sequence.

[0037] Among all quantum barrier layers in the light-emitting layer 100, the first quantum barrier layer 101 is the thickest. This setting can adjust the transition efficiency of carriers, so that carriers can be efficiently transported, reduce the loss of excess hot carriers, and improve the internal quantum efficiency as much as possible; improve the number of carriers in the upper and lower energy levels of the light-emitting region in the active region, and obtain a good population inversion effect.

[0038] The first quantum well layer 102 is adjacent to the first quantum barrier layer 101, and the first quantum well layer 102 includes two Ga component materials, and the Ga component ratio in each Ga component material is 38%-47%. The ratio of Ga in the two Ga component materials is adjusted according to the required wavelength and the stress of the overall material, so as to realize the transition of a part of the carriers, and provide a part of the design for the multi-channel of the lower energy level, and provide freedom for the extension of the energy band. In a possible implementation, in the first quantum well layer 102, the Ga component ratio in the Ga component material close to the first quantum barrier layer 101 is 47%, and the Ga component ratio in the Ga component material close to the second quantum barrier layer 103 is 38%-46%. Exemplarily, the first quantum well layer 102 contains two components of InGaAs, which can be In0.56Ga0.44As and In0.53Ga0.47As.

[0039] The second quantum barrier layer 103 is adjacent to the first quantum well layer 102. The second quantum barrier layer 103 includes two Al component materials, and the Al component ratio of each Al component material is 55%-68%. In a possible implementation, the second quantum barrier layer 103 includes two components of InAlAs, specifically In0.33Al0.67As and In0.52Al0.48As. An AIAs intercalation layer 1031 is provided between the two Al component materials.

[0040] The tunneling escape rate of carriers in a quantum well is expressed as τ-1, which is proportional to Wherein Lb is the thickness of the second quantum barrier layer 103, m is the effective mass of electrons in the second quantum barrier layer 103, H is the effective barrier height of carrier electrons, and h is Planck's constant. It can be seen from the expression that if Lb, mb, and H remain unchanged, the probability of electron tunneling through the exit barrier can remain unchanged. In the present embodiment, this is achieved by adjusting the thickness of the three materials of the second quantum barrier layer 103, which can further hinder the leakage of hot carriers. The second quantum barrier layer 103 can improve the internal quantum efficiency of short-wave quantum cascade lasers. One of the main factors limiting the performance of quantum cascade lasers is its low internal quantum efficiency. From the perspective of energy bands, parasitic upper energy levels are inevitably present in the active region. The electrons injected into the region in the previous cycle have a certain probability of transitioning to the parasitic energy level, causing the leakage of carriers. The introduction of the AIAs intercalation layer 1031 can increase the energy interval AE between the parasitic energy level and the upper energy level by about 30meV, thereby reducing the probability of carriers escaping to the parasitic energy level and improving the injection efficiency; it is conducive to improving the temperature characteristics of quantum cascade lasers. As the operating temperature of the laser increases, the probability of carriers in the active region thermally escaping to the continuous state across the conduction band step increases, and the slope efficiency and threshold current density of the laser degrade accordingly until it cannot work. The introduction of the AIAS layer increases the height of the continuous state in the injection region, thereby reducing the probability of thermal escape of carriers and increasing the operating temperature of the device, which is more promising in extreme working environments.

[0041] The second quantum well layer 104 is adjacent to the second quantum barrier layer 103, and the second quantum well layer 104 includes a component material having strained InGaAs. The quantum well barrier in the injection region satisfies the Bragg reflection condition, while reducing the logarithm of the well barrier and increasing the efficiency of transmission. The lower laser state includes multiple states (mini-bands), in which the wave function extends to the entire active injector portion. At least three final energy levels (1, 1' and 1") are used for downward transitions from energy level 2; the energy level spacing E of the lower energy band mentioned above 21 Much smaller than E Lo , energy level interval E 11’ It is also much smaller than E Lo , E 21’The interval between energy level 1 and energy level 2 is not equal to the interval between energy level 1 and energy level 1', which is based on the combination of four components, but they are all very small, about 5meV to 10meV, so that the carrier wave function of energy level 1 overlaps with the carrier wave function of energy level 2. Similarly, the carrier wave function of energy level 1' overlaps with the carrier wave function of energy level 2, which significantly prevents the thermal backfill effect. This structure effectively improves the voltage efficiency and promotes the improvement of the WPE of the QCL. At the same time, this design makes the structural design flexible. Each energy level 1, 1' has a non-uniform square wave function distribution, which can promote the rapid transfer of carriers. In this design, the transition occurs between state 4 and state 3 to the mini-band, and the multi-transition channel leads to a wide gain spectrum.

[0042] The third quantum barrier layer 105 is adjacent to the second quantum well layer 104, and the third quantum barrier layer 105 comprises strained InAlAs, which satisfies the Bragg reflection condition. For example, the third quantum barrier layer 105 may be In0.33Al0.67As and In0.52Al0.48As.

[0043] The third quantum well layer 106 is adjacent to the third quantum barrier layer 105. The third quantum well layer 106 has the same composition and thickness as the first quantum well layer 102, and can adjust the transport channel of the carriers at the lower energy level, realize multi-channel carrier channels as much as possible, and improve the flexibility of the design for the overall strain compensation. Exemplarily, the third quantum well layer 106 includes two components of InGaAs, specifically In0.56Ga0.44As and In0.53Ga0.47As.

[0044] Please continue to see Figure 1Compared with the light-emitting area, the design of the injection area is more flexible. The thickness of the injection layer 200 is between 2.0nm and 4.0nm. It is necessary to ensure the carriers while paying attention to designing the voltage defect as small as possible to reduce the thermal backfill of the carriers, especially the design of the last quantum well of the injection layer 200 away from the light-emitting area, that is, the end quantum well layer 201. It is very important to consider the injection efficiency of the carriers in the injection area from the last potential well to the barrier between the next cycle. The effects of the injection efficiency η3 and η2 are obviously asymmetric. The gain is scaled only by the value of η3, and according to the ratio of τ2 / τ3, the value of η2 may have a more significant effect on reducing the gain. Obviously, although the design should strive to make the injection efficiency close to the ideal value in principle, the adverse effects of non-ideal injection efficiency can be alleviated by a system with a large lifetime ratio (τ2 / τ3). The above clearly shows the strong dependence of the gain on the injection efficiency and the lifetime ratio: the injection region must be designed to maximize the difference, for example, when designing the efficient active region injection region, the difference η3τ3-η2τ2 is maximized and the ratio τ2 / τ32 is minimized; where η3 represents the injection energy level E inj The injection efficiency to the next energy level E3, η3 represents the injection energy level E inj The injection efficiency to the next energy level E2, τ3 refers to the lifetime of E3 carriers, τ32 represents the lifetime of carriers on E3 transitioning to E2, and τ2 refers to the lifetime of E2 carriers.

[0045] This embodiment also provides a high-power long-wave quantum cascade laser, including an upper waveguide layer, a lower waveguide layer, and an active region disposed between the upper waveguide layer and the lower waveguide layer, wherein the active region includes at least one of the above-mentioned laser active regions. When the active region includes multiple active regions, the multiple active regions are superimposed to form the active region. Exemplarily, the number of active regions in the active region may be 30, 40, or 50.

[0046] In the quantum cascade laser, the active region is composed of a strain compensation system, including In0.56Ga0.44As, In0.33Al0.67As, In0.53Ga0.47As, In0.52Al0.48As and AlAs. Conventional infrared long-wave quantum cascade lasers are designed and manufactured using lattice-matched In0.43Ga0.57As / In0.42Al0.58As compositions, which have a relatively small band offset of 520 meV; if the emission wavelength of the light-emitting layer is 9 um, this band offset results in an energy interval of 250 meV between the upper laser level and the continuous state located above the barrier; the band offset of the lattice-matched composition is not sufficient to fully utilize the smaller transition energy of the long-wave infrared quantum cascade laser to suppress carrier leakage from the upper laser state. This embodiment adopts strain to make the band shift sufficient to fully utilize the smaller transition energy of the long-wave infrared quantum cascade laser to suppress the carrier leakage from the upper laser state, thereby improving the WPE of the long-wave infrared quantum cascade laser. According to experiments, this scheme can achieve a band step shift of 1.53eV.

[0047] In a possible implementation, in the quantum cascade laser, the active layer includes a light-emitting layer 100 and an injection layer 200. The light-emitting layer 100 includes a quantum barrier layer and a quantum well layer. The thickness of all quantum well layers in the active region is between 2.7nm and 6.0nm. The quantum barrier layer of the AlAs intercalation layer should be as small as possible from 0.058nm. At the same time, the Al component of the quantum barrier layer described is higher than the Al component of the conventional matching infrared long-wave quantum cascade laser. According to such a quantum barrier layer, the high proportion of the Al component leads to a high barrier potential in the system, which is conducive to suppressing the leakage of high-temperature and low-energy carriers across the barrier. The average width of the quantum well layer (In0.56Ga0.44As) is mainly between 3.0nm and 4.0nm. The quantum well layer (In0.53Ga0.47As) is mainly selectively inserted into the quantum well layer of the existing light-emitting layer, the purpose of which is to flexibly adjust the wavelength change, and at the same time, it can also be used as a matching material structure to improve the quality of the material and reduce the interface roughness.

[0048] In one possible implementation, in the described quantum cascade laser, the first quantum barrier layer 101 of the light-emitting layer in the active region is the thickest quantum barrier layer in the entire light-emitting region. Immediately following the first quantum well layer 102 is a first barrier layer comprising two Ga component materials, and the combination of Ga components is adjusted according to the required wavelength and the stress of the overall material. The second quantum barrier layer 103 is a combination of two Al component materials, with an AlAs intercalation layer 1031 in the middle. The Al component barrier with a sandwich structure can further hinder the leakage of hot carriers. The last layer of the light-emitting region is the third quantum well layer 106, which uses a component with strained InGaAs. The quantum well barrier in the injection region meets the Bragg reflection condition, while reducing the logarithm of the well barrier and increasing the transmission efficiency. The lower laser state includes multiple states (mini bands) in which the wave function extends to the entire active injector portion. At least three final energy levels (1, 1' and 1") are used for downward transitions from energy level 2; the energy level spacing E of the lower partial energy band mentioned above 21 Much smaller than E Lo , energy level interval E 11’ It is also much smaller than E Lo , E 21’ The interval between energy level 1 and energy level 2 is not equal to the interval between energy level 1 and energy level 1', which is based on the combination of the four components, but is very small, about 5meV to 10meV, so that the carrier wave function of energy level 1 overlaps with the carrier wave function of energy level 2. Similarly, the carrier wave function of energy level 1' overlaps with the carrier wave function of energy level 2, which significantly prevents the thermal backfill effect and effectively improves the voltage efficiency, thereby promoting the improvement of the WPE of the QCL. At the same time, this design makes the structural design more flexible. Each energy level 1 and 1' has a non-uniform square wave function distribution, which can promote the rapid transfer of carriers; in this design, the transition occurs between state 4 and state 3 to the mini-band, so that many transition channels lead to a wide gain spectrum, which is very beneficial for the actual wide tuning environment.

[0049] The above quantum cascade laser can be prepared based on MOCVD. MOCVD is the full name of metal organic compound vapor phase epitaxy technology, which is the basic technology for manufacturing most optoelectronic materials. MOCVD equipment is a means of research and production of compound semiconductor materials, especially as an industrial production equipment. Its high quality, stability, repeatability and scale are irreplaceable by other semiconductor material growth equipment. The MOCVD method used in the present invention is as follows:

[0050] S1. All structures were grown using MOCVD in a low pressure (100 mbar) environment. Group III precursors were trimethyl indium (TMIn, In(CH3)3), trimethyl gallium (TMGa, Ga(CH3)3), trimethyl aluminum (TMAl, Al(CH3)3) and triethyl gallium (TEGa, Ga(C2H5)3), and group V precursors were arsine (AsH3) and phosphine (PH3). The n-type dopant precursor was diluted monosilane (SiH4) balanced in hydrogen (0.02% in H2). Quantum cascade lasers were grown on InP substrates (n-doped (Si, 2×10 17 cm -3 )). The epitaxial growth temperature is 500–700°C. The growth rate of the QCL active region is between 0.1–0.5nm / s, and the growth rate of the waveguide and cap layer (n-doped InP) is 0.3–0.8nm / s. The V / III ratio is 15–200.

[0051] S2. After growing the lower waveguide InP, raise the temperature to 680 degrees, open the TMGa and TMAl sources into the reaction chamber respectively, maintain the flow of TMGa and TMAl sources constant, and follow Figure 2 The active region structure shown in the figure calculates the growth time T of each layer of In0.56Ga0.44As InGaAs , and the growth time T of each layer of In0.369Al0.631As InAlAs , according to Figure 2 The described order and the growth time of each layer of material were followed by orderly switching of the TMGa and TMAl sources and maintaining the flow rates of the TMGa and TMAl sources constant. All MO sources were turned off after 55 growth cycles.

[0052] S3, then cool down to 600 degrees, turn on the TMIn and PH3 sources and keep their flow rates constant, in order to grow the lower waveguide for 5 and a half hours.

[0053] S4. Then turn off all MO sources and cool down to room temperature.

[0054] S5. After the growth is completed, the grown material is characterized and the manufacturing process and device verification are performed.

[0055] HRXRD is very sensitive in assessing the overall MQW structure and the quality of the heterointerfaces. Structural studies were performed by HRXRD measurements. Figure 3 XRD θ_2ω scan and corresponding simulation display of the QCL epitaxial structure. Figure 3 The full width at half maximum (FWHM) of the satellite diffraction peaks is shown marked, which is given by fitting the peaks with a Gaussian distribution. High-resolution X-ray diffraction rocking curves, such as Figure 3As shown, high-resolution superlattice peaks up to the 15th order are revealed, indicating high structural quality and periodicity. The full width at half maximum (FWHM) of the satellite diffraction peaks and the inter-satellite interference fringes is a measure of the overall material quality. It also shows that the heterostructure is of high quality, with the bandwidth of the main satellite peaks being 13-17arcsec. In particular, the FWHM of the zero-order peak is only 17arcsec. The narrow FWHM of the measured scan indicates consistent periodicity from the initially grown layer to the uppermost surface. The above narrow satellite peaks also mean that the interface roughness (IFR) is small. This ensures high performance of the QCL. At the same time, the QCL phase period measured from the satellite peak spacing is 44.8nm, which is very close to the nominal value of 45.1nm. The closeness of the simulation and experimental data also shows that the layer thickness, material composition and interface switching are excellently uniform and controlled throughout the 55-period layer structure.

[0056] like Figure 4 The AFM image of the scanned sample is shown, and the test area size is 1μm×1μm. The image shows that the step edge is smooth, and the atomic step is very obvious, about 210nm. From the overall point of view, it can be seen that both samples have obvious step flow style surface morphology, and the surface growth morphology is good. And changing the growth order of the active area has no obvious effect on the surface morphology of the sample.

[0057] The long-wave (9-10 μm) quantum cascade laser was prepared by double-channel injection process. The PIV curve of its pulse peak is as follows: Figure 5 See Figure 5 , the temperature changes from 283K to 333K, and the electro-optical conversion efficiency changes from 5.9% to 4%. As the temperature rises, its electro-optical conversion efficiency decreases relatively slowly, indicating that the device is not sensitive to temperature. The temperature changes from 283K to 333K, and the peak output power changes from 2200mW to 1600mW. The overall power decrease is not much, and as the temperature rises, the added power per unit current (slope efficiency) is roughly the same, indicating that within the power-on range, under the same power consumption, the proportion of electricity converted to light is large. Although Figure 5 The displayed electro-optical conversion efficiency is only 5.9%, but once the laser is prepared as a semi-insulating InP buried process and good heat dissipation treatment is done, a higher electro-optical conversion efficiency can be obtained, reaching 8%-10%.

[0058] Figure 6 is the room temperature electroluminescence spectrum of a specific long-wave (9-10μm) quantum cascade laser sample. Figure 6 After performing Lorentz fitting on the measured data, two Lorentz peaks can be seen. Each Lorentz peak corresponds to a cluster of energy levels. The half-height widths of the two Lorentz peaks are 90 cm -1 and 314cm -1The sum of these two half-height widths is 404cm -1 , at least 200cm beyond conventional lasers -1 , which is twice the half-width of the conventional long-wave QCLEL spectrum, indicating that the quantum cascade laser of this embodiment has a wide gain characteristic. Figure 5 , indicating that this scheme not only obtains a wide gain spectrum but also obtains high-power performance characteristics, which is conducive to the preparation of a 400cm -1 The above room temperature continuous long-wave width-tunable laser provides possibilities, which is of great significance to national security and defense security. For example, the wide gain and high power characteristics of the laser can be used to detect bombs in battlefield environments based on the principles of laser spectroscopy, because macromolecules such as TNT and VOC are all located between 7-10μm; in terms of national security, it can be used for luggage testing at airports and railway stations and document testing on gates to detect whether dangerous explosive items are carried.

[0059] Note that the above are only preferred embodiments of the present invention and the technical principles used. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments, and may include more other equivalent embodiments without departing from the concept of the present invention, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A laser active region, characterized in that: The invention comprises a light-emitting layer and an injection layer, wherein the light-emitting layer and the injection layer respectively have a quantum well structure in which quantum potential well layers and quantum potential barrier layers are alternately stacked; the emission wavelength of the light-emitting layer is 8 μm-12 μm, and satisfies the emission of oblique transition; The light-emitting layer includes a first quantum barrier layer, a first quantum well layer, a second quantum barrier layer, a second quantum well layer, a third quantum barrier layer and a third quantum well layer which are arranged in sequence; among all the quantum barrier layers of the light-emitting layer, the first quantum barrier layer is arranged to be the thickest to improve the carrier transport efficiency; the first quantum well layer contains two Ga component materials, and the Ga component ratio of each Ga component material is 38%-47%; the second quantum barrier layer contains two Al component materials, and the Al component ratio of each Al component material is 55%-68%.

2. The laser active region according to claim 1, characterized in that: In the first quantum well layer, the Ga component ratio in the Ga component material close to the first quantum barrier layer is 47%, and the Ga component ratio in the Ga component material close to the second quantum barrier layer is 38%-46%.

3. The laser active region according to claim 1, characterized in that: In the second quantum barrier layer, an AIAs intercalation layer is provided between two Al component materials of the second quantum barrier layer.

4. The laser active region according to claim 1, characterized in that: The second quantum well layer includes a component material having strained InGaAs; the third quantum barrier layer includes strained InAlAs; and the third quantum well layer includes two components of InGaAs.

5. The laser active region according to claim 1, characterized in that: The injection layer is designed based on maximizing the difference η3τ3-η2τ2 and minimizing the ratio τ2 / τ32, where η3 represents the injection energy level E inj The injection efficiency to the next energy level E3, η2 represents the injection energy level E inj The injection efficiency to the next energy level E2, τ3 refers to the lifetime of E3 carriers, τ32 represents the lifetime of carriers on E3 transitioning to E2, and τ2 refers to the lifetime of E2 carriers.

6. The laser active region according to claim 1, characterized in that: The injection layer has a thickness of 2.0 nm to 4.0 nm.

7. The laser active region according to claim 3, characterized in that: The two Ga component materials contained in the first quantum well layer are In0.56Ga0.44As and In0.53Ga0.47As.

8. The laser active region according to claim 3, characterized in that: The second quantum barrier layer contains two Al component materials, namely, In0.33Al0.67As and In0.52Al0.48As.

9. The laser active region according to claim 1, characterized in that: The tensile strain and compressive strain of the active region are equal; the injection layer satisfies kw / Hw+kb / Hb=π, kw is the wave vector of the wave function in the quantum potential well layer of the injection layer, kb is the wave vector of the wave function in the quantum potential barrier layer of the injection layer, Hw is the width of the quantum potential well layer of the injection layer, and Hb is the width of the quantum barrier layer of the injection layer.

10. A high-power long-wave quantum cascade laser, characterized in that: The invention comprises an upper waveguide layer, a lower waveguide layer and an active region arranged between the upper waveguide layer and the lower waveguide layer, wherein the active region comprises at least one laser active region according to any one of claims 1 to 9.

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