TWI787646B - Ultraviolet c light-emitting diode - Google Patents

Abstract

An ultraviolet C light-emitting diode including an n-type semiconductor layer, a p-type semiconductor layer, an active layer, a two-dimensional hole gas (2DHG) inducing layer, and an electron blocking layer is provided. The active layer is disposed between the n-type semiconductor layer and the p-type semiconductor layer, wherein a wavelength of a maximum peak of a spectrum emitted by the active layer ranges from 230 nm to 280 nm. The 2DHG inducing layer is disposed between the active layer and the p-type semiconductor layer. A concentration of magnesium in the 2DHG inducing layer is less than 10¹⁷ atoms/cm³. The electron blocking layer is disposed between the p-type semiconductor layer and the 2DHG inducing layer. A concentration of magnesium in a part of the electron blocking layer adjacent to the 2DHG inducing layer is greater than 10¹⁹ atoms/cm³.

Description

UV-C Light Emitting Diodes

This technical field relates to a kind of ultraviolet C light-emitting diode.

In order to allow hole carriers to be easily injected into the light-emitting layer, active layer or multiple quantum well layer, the electron blocking layer (electron blocking layer) in the ultraviolet C light-emitting diode (UVC-LED) structure , EBL) will form a P-type semiconductor by doping beryllium, magnesium or zinc. In this way, in addition to increasing the hole concentration, the efficiency of the UV-C light-emitting diode device can be further improved.

But when beryllium, magnesium or zinc etc. are doped in the electron blocking layer, because the aluminum concentration in the electron blocking layer is higher than the aluminum concentration in the quantum energy barrier in the light-emitting layer, the active layer or the multiple quantum well layer, making the beryllium , magnesium or zinc are not easily doped. On the other hand, if the doping amount of beryllium, magnesium, or zinc is increased, the problem faced is the memory effect of beryllium, magnesium, zinc, etc. and their diffusion into quantum wells or quantum energy barriers. As a result, excessive impurities will form defects in the quantum wells or quantum energy barriers, resulting in a decrease in the luminous efficacy of the UV-C light-emitting diode device and unnecessary defect emission.

An embodiment of the present disclosure provides a UV-C light-emitting diode, which includes an N-type semiconductor layer, a P-type semiconductor layer, an active layer, a first electron blocking layer, and a second electron blocking layer. The active layer is located between the N-type semiconductor layer and the P-type semiconductor layer, the wavelength of the maximum peak of the spectrum emitted by the active layer falls within the range of 230 nm to 280 nm, and the concentration of magnesium in the active layer is less than 10 ¹⁷ Atoms/cubic centimeter. The first electron blocking layer and the second electron blocking layer are located between the P-type semiconductor layer and the active layer, the concentration of magnesium in the second electron blocking layer is greater than the concentration of magnesium in the first electron blocking layer, and the second electron blocking layer The concentration of magnesium in it is greater than 10 ¹⁸ atoms/cubic centimeter.

An embodiment of the present disclosure proposes a UV-C light-emitting diode, including an N-type semiconductor layer, a P-type semiconductor layer, an active layer, and a two-dimensional hole gas inducing layer (two-dimensional hole gas inducing layer, 2DHG inducing layer) and an electron blocking layer. The active layer is disposed between the N-type semiconductor layer and the P-type semiconductor layer, wherein the maximum peak wavelength of the spectrum emitted by the active layer falls within the range of 230 nm to 280 nm. The two-dimensional hole gas inducing layer is configured between the active layer and the P-type semiconductor layer. The material of the two-dimensional hole gas induction layer includes Al _α Ga _β N, wherein β=1-α, and the concentration of magnesium in the two-dimensional hole gas induction layer is less than 10 ¹⁷ atoms/cm3. The electron blocking layer is configured between the P-type semiconductor layer and the two-dimensional hole gas inducing layer. The material of the electron blocking layer includes Al _γ Ga _δ N, where δ=1-γ, 0.65<γ≦0.9, and the concentration of magnesium in the part of the electron blocking layer adjacent to the two-dimensional hole gas induction layer is greater than 10 ¹⁹ atoms / cubic centimeter. The UV-C light-emitting diode conforms to α>γ and 0.1<α-γ≦0.3, so that two-dimensional hole gas is formed at the interface between the two-dimensional hole gas induction layer and the electron blocking layer.

In order to make the above-mentioned features and advantages of the present disclosure more comprehensible, the following specific embodiments are described in detail together with the accompanying drawings.

50: first electrode

60: Second electrode

100, 100a, 100b, 100c, 100d: ultraviolet C light-emitting diodes

110: N-type semiconductor layer

112: the first N-type aluminum gallium nitride layer

114: the second N-type aluminum gallium nitride layer

120, 120d: P-type semiconductor layer

122: the first p-type gallium nitride or aluminum gallium nitride layer

122d: Aluminum gradient layer

124: the second p-type gallium nitride or aluminum gallium nitride layer

124d: P-type semiconductor sublayer

130: active layer

132: Barrier layer

134: energy well layer

140: Two-dimensional hole gas induced layer

160: sapphire substrate

170: Aluminum nitride template layer

180: buffer layer

190: Unintentionally doped AlGaN layer

200, 200a, 200b, 200c, 200d: electron blocking layer

210, 210c, 210d: first electron blocking layer

212: The first sublayer

214: second sublayer

220, 220d: the second electron blocking layer

E _c : the lowest energy level of the conduction band

Ef _n : Fermi level of N-type semiconductor

Ef _p : Fermi level of P-type semiconductor

E _v : the highest energy level of the valence band

p: hole density

P1: the first luminescent peak

P2: Second Luminous Peak

Q1, Q2: points

T1, T11, T12, T2, T2a, T2b, T3, T4: Thickness

ΔE _c : energy barrier height difference

FIG. 1 is a schematic cross-sectional view of a UV-C light-emitting diode according to an embodiment of the present disclosure.

Fig. 2 is a composition distribution diagram obtained by measuring the ultraviolet C light-emitting diode in Fig. 1 with a secondary ion mass spectrometer.

FIG. 3 is a spectrum diagram of the ultraviolet C light-emitting diode in FIG. 1 .

FIG. 4 is an energy band diagram of a UV-C light-emitting diode in a comparative example.

FIG. 5 is an energy band diagram of the UV-C light-emitting diode in FIG. 1 .

FIG. 6 is a schematic cross-sectional view of a UV-C light-emitting diode according to another embodiment of the present disclosure.

FIG. 7 is a composition distribution diagram obtained by measuring a UV-C light-emitting diode of a comparative example by using a secondary ion mass spectrometer.

FIG. 8 is a spectrum diagram of the UV-C light-emitting diode of the comparative example in FIG. 7 .

FIG. 9 is a composition distribution diagram obtained by measuring a UV-C light-emitting diode according to another embodiment of the present disclosure by using a secondary ion mass spectrometer.

FIG. 10 is a spectrum diagram of the ultraviolet C light-emitting diode of the embodiment corresponding to FIG. 9 .

FIG. 11 is a schematic cross-sectional view of a UV-C light-emitting diode according to another embodiment of the present disclosure.

FIG. 12 is a schematic cross-sectional view of a UV-C light-emitting diode according to yet another embodiment of the present disclosure.

FIG. 13 is a schematic cross-sectional view of a UV-C light-emitting diode according to another embodiment of the present disclosure.

FIG. 14 is a composition distribution diagram obtained by measuring the ultraviolet C light-emitting diode in FIG. 13 by using a secondary ion mass spectrometer.

FIG. 15 is an energy band diagram of the UV-C light-emitting diode in FIG. 13 .

FIG. 16A is a graph showing the carrier injection efficiency of the UV-C light-emitting diode of FIG. 13 relative to α-γ when the magnesium concentration of the electron blocking layer is 10 ¹⁹ atoms/cm3.

16B is a graph showing the carrier injection efficiency of the UV-C light-emitting diode in FIG. 13 relative to α-γ when the magnesium concentration of the electron blocking layer is 10 ²⁰ atoms/cm3.

FIG. 17 is a transmission electron microscopy image of the UV-C LED of FIG. 13 .

FIG. 1 is a schematic cross-sectional view of a UV-C light-emitting diode according to an embodiment of the present disclosure. Referring to FIG. 1 , the UV-C light emitting diode 100 of this embodiment includes an N-type semiconductor layer 110 , a P-type semiconductor layer 120 , an active layer 130 (or multiple quantum wells) and an electron blocking layer 200 . The N-type semiconductor layer 110 is, for example, an N-type The aluminum gallium nitride layer may have a group IVA doping source (such as carbon or silicon), and this group IVA doping source is used to replace aluminum or gallium atoms, and more free electrons, or may have a group VIA element The doping source, the doping source of the VIA group element is used to replace the nitrogen atom, so as to generate more free electrons, or it may have the doping source of other elements, which has the characteristics of generating more free electrons after replacing aluminum, gallium and nitrogen. In this embodiment, the UV-C light-emitting diode 100 further includes a sapphire substrate 160, an aluminum nitride template layer 170, a buffer layer 180, and an unintentionally doped aluminum gallium nitride layer (unintentionally doped aluminum gallium nitride layer) 190 , wherein the aluminum nitride template layer 170 , the buffer layer 180 , the unintentionally doped aluminum gallium nitride layer 190 and the N-type semiconductor layer 110 are sequentially stacked on the sapphire substrate 160 . The material of the buffer layer 180 is, for example, aluminum gallium nitride, the cation mole fraction of aluminum is in the range of 95% to 50%, and the cation mole fraction of gallium is in the range of 5% to 50%. Alternatively, the buffer layer 180 may be an aluminum gallium nitride layer having a superlattice structure, the cation mole fraction of aluminum is in the range of 95% to 50%, and the cation mole fraction of gallium is in the range of 5% to 50%. 50%.

In this embodiment, the N-type semiconductor layer 110 includes a first N-type AlGaN layer 112 and a second N-type AlGaN layer 114, wherein the N-type of the first N-type AlGaN layer 112 The doping concentration is higher than the N-type doping concentration of the second N-type AlGaN layer 114, and the second N-type AlGaN layer 114 and the first N-type AlGaN layer 112 are sequentially stacked on an unintentional AlGaN layer 190 is doped.

The active layer 130 is a light-emitting layer. In this embodiment, the active layer 130 is a multiple quantum well layer, which includes a plurality of energy barrier layers (barrier layers) 132 and energy well layers (well layers) stacked alternately on the N-type semiconductor layer 110. layer) 134. In this example, Both the energy barrier layer 132 and the energy well layer 134 are made of AlGaN, but the aluminum concentration in the energy barrier layer 132 is higher than the aluminum concentration in the energy well layer 134 .

The electron blocking layer 200 includes a first electron blocking layer 210 and a second electron blocking layer 220 . In this embodiment, the first electron blocking layer 210 and the second electron blocking layer 220 are sequentially stacked on the active layer 130 . The first electron blocking layer 210 and the second electron blocking layer 220 are, for example, aluminum gallium nitride layers doped with magnesium, wherein the concentration of magnesium in the second electron blocking layer 220 is greater than the concentration of magnesium in the first electron blocking layer 210 , and the concentration of magnesium in the second electron blocking layer 220 is greater than 10 ¹⁸ atoms/cm3.

The P-type semiconductor layer 120 is stacked on the electron blocking layer 200 . In this embodiment, the P-type semiconductor layer 120 includes a first P-type GaN or AlGaN layer 122 and a second P-type GaN or AlN layer stacked on the electron blocking layer 200 in sequence. Gallium layer 124 , wherein the P-type doping concentration of the second P-type GaN or AlGaN layer 124 is higher than the P-type doping concentration of the first P-type GaN or AlGaN layer 122 . The p-type doping in the first p-type gallium nitride or aluminum gallium nitride layer 122 and the second p-type gallium nitride or aluminum gallium nitride layer 124 can be group IIA elements, such as beryllium or magnesium, and in this In the embodiment, magnesium is taken as an example.

In this embodiment, the active layer 130 is located between the N-type semiconductor layer 110 and the P-type semiconductor layer 120, and the wavelength of the maximum peak of the spectrum emitted by the active layer 130 falls within the range of 230 nm to 280 nm, also It falls within the wavelength band of ultraviolet C. The ultraviolet light waveband includes ultraviolet light A (ultraviolet A, UVA) waveband, ultraviolet light B (ultraviolet B, UVB) waveband and ultraviolet light C (ultraviolet C, UVC) waveband. The wavelength range of the ultraviolet A band is about 400 nm to 315 nm, that is, the photon energy range is about 3.10 eV to 3.94 eV. The wavelength range of the ultraviolet B-band is about 315 nm to 280 nm, that is, the photon energy range is about 3.94 eV to 4.43 eV. The wavelength range of the ultraviolet C-band is about 280 nm to 100 nm, that is, the photon energy range is about 4.43 eV to 12.4 eV. The concentration of magnesium in the active layer 130 is less than 10 ¹⁷ atoms/cm3. In addition, the first electron blocking layer 210 and the second electron blocking layer 220 are located between the P-type semiconductor layer 120 and the active layer 130 . In this embodiment, the second electron blocking layer 220 is located between the first electron blocking layer 210 and the P-type semiconductor layer 120 .

The UV-C light-emitting diode 100 of this embodiment may further include a first electrode 50 and a second electrode 60, wherein the first electrode 50 is electrically connected to the N-type semiconductor layer 110, and the second electrode 60 is electrically connected to the P-type semiconductor layer 110. The semiconductor layer 120 is electrically connected. By applying a forward bias voltage to the first electrode 50 and the second electrode 60 , the active layer 130 of the UV-C light-emitting diode 100 can emit C-band UV light through radiative recombination. In FIG. 1 , the first electrode 50 and the second electrode 60 are arranged horizontally as an example, that is, the first electrode 50 and the second electrode 60 are located on the same side of the UV-C light-emitting diode 100 . However, in other embodiments, the first electrode 50 and the second electrode 60 can also be arranged vertically, that is, the first electrode 50 is located under the N-type semiconductor layer 110, and the second electrode 60 is located under the P-type semiconductor layer 110. above the semiconductor layer 120 .

In the ultraviolet C light-emitting diode 100 of this embodiment, since the concentration of magnesium in the second electron blocking layer 220 is greater than the concentration of magnesium in the first electron blocking layer 210, and in the second electron blocking layer 220 The concentration of magnesium is greater than 10 ¹⁸ atoms/cm3, so through doping magnesium in a specific ratio, the overflow of electrons in the active layer 130 to the P-type semiconductor layer 120 can be effectively suppressed, thereby improving the ultraviolet C Device performance of the light emitting diode 100 . In addition, in the UV-C light-emitting diode 100 of this embodiment, by adjusting the appropriate molar fraction of aluminum cations in the electron blocking layer 200 and the appropriate amount of magnesium doping, in addition to blocking electrons from overflowing to In addition to the P-type semiconductor layer 120 , the efficiency of hole carrier injection into the active layer 130 can also be improved, thereby increasing the luminous efficacy of the UV-C light-emitting diode 100 .

In this embodiment, the thickness T2 of the second electron blocking layer 220 is in the range of 0.1 nm to 20 nm, and the thickness T1 of the first electron blocking layer 210 is in the range of 10 nm to 100 nm. within range.

Fig. 2 is a composition distribution diagram obtained by measuring the UV-C light-emitting diode in Fig. 1 by secondary ion mass spectrometer (secondary ion mass spectrometer, SIMS), and Fig. 3 is the spectrum of the UV-C light-emitting diode in Fig. 1 picture. Please refer to FIG. 1 to FIG. 3 , the spectrum of the light emitted by the ultraviolet C light-emitting diode 100 of this embodiment includes a first luminescence peak P1 and a second luminescence peak P2, and the spectral intensity of the first luminescence peak P1 It is more than 20 times the spectral intensity of the second luminescence peak P2. In FIG. 3 , the second luminescence peak P2 is not obvious, but if the vertical axis (ie spectral intensity) is taken as a logarithmic value, the second luminescence peak P2 can be clearly seen. This is because the difference between the spectral intensity of the first luminescence peak P1 and the spectral intensity of the second luminescence peak P2 is too large, so that the second luminescence peak P2 cannot be seen in Figure 3, but the second luminescence can be made after taking the logarithmic value on the vertical axis. Peak P2 becomes apparent. In this embodiment, the difference obtained by subtracting the wavelength of the first luminescence peak P1 from the wavelength of the second luminescence peak P2 falls within 20 nanometers to 40 nanometers. within the range of meters. The second luminescence peak P2 is produced by defect luminescence. It can be clearly seen from FIG. Good luminous efficacy.

In this embodiment, the highest magnesium concentration in the second electron blocking layer 220 (for example, the magnesium concentration at Q1 in FIG. 2 is the lowest magnesium concentration in the first electron blocking layer 210 (for example, the magnesium at Q2 in FIG. 2 Concentration) 5 to 200 times, another embodiment is 20 to 80 times.In addition, in this embodiment, the magnesium concentration in the second electron blocking layer 220 is 1/2 of the magnesium concentration in the P-type semiconductor layer 120 to 1/50 times. In addition, in this embodiment, the distribution curve of the overall magnesium concentration of the first electron blocking layer 210 and the second electron blocking layer 220 from the P-type semiconductor 120 to the active layer 130 presents a steep drop first and then a gentle Then the appearance of the steep drop is shown in Figure 2.

In this embodiment, the cation mole fraction of aluminum in the first electron blocking layer 210 and the second electron blocking layer 220 falls within a range of 60% to 80%. For example, when the chemical formula of the main components of the first electron blocking layer 210 and the second electron blocking layer 220 can be expressed as AlxGa1 _{-xN ,} then x in this chemical formula is the cation mole fraction of the above-mentioned aluminum Rate.

In this embodiment, the refractive index of the second electron blocking layer 220 is smaller than the refractive index of the energy well layer 134 of the active layer 130 and smaller than the refractive index of the energy barrier layer 132 of the active layer 130 . In addition, the refractive index of the first electron blocking layer 210 is also lower than the refractive index of the energy well layer 134 of the active layer 130 , and is smaller than the refractive index of the energy barrier layer 132 of the active layer 130 . Generally speaking, in AlGaN materials, the higher the aluminum content, the smaller the refractive index.

In the UV-C light-emitting diode 100 of this embodiment, since the second electron blocking layer 220 is located between the first electron blocking layer 210 and the P-type semiconductor layer 120, magnesium can be effectively doped in the second electron blocking layer 220. In the barrier layer 220 , magnesium will not diffuse into the active layer 130 in a gradient distribution manner. In this way, defect luminescence induced by magnesium entering the active layer 130 can be effectively reduced, thereby improving the luminous efficiency of the UV-C light-emitting diode 100 . In this embodiment, the luminous intensity or light output power of the UV-C LED 100 is 17.4 milliwatts.

FIG. 4 is an energy band diagram of a UV-C light-emitting diode in a comparative example, and FIG. 5 is an energy-band diagram of the UV-C light-emitting diode in FIG. 1 . Please refer to FIG. 1, FIG. 4 and FIG. 5, the structure of the UV-C light-emitting diode corresponding to FIG. 4 and FIG. 5 can be the same as the structure of the UV-C light-emitting diode 100 in FIG. The difference is that the magnesium concentration in the electron blocking layer 200 in FIG. 4 is about 5×10 ¹⁷ atoms/cm3, while the magnesium concentration in the electron blocking layer 200 in FIG. 5 is about 5×10 ¹⁸ atoms/cm3 cm. In Figure 4 and Figure 5, the curve corresponding to E _c is the lowest energy level of the conduction band (conduction), the curve corresponding to Ef _n is the quasi-fermienergy level of electrons, and the curve corresponding to E _v The curve of is the highest energy level of the valence band, and the curve corresponding to Ef _p is the quasi-Fermi level of the hole. 4 and 5, when the magnesium concentration in the electron blocking layer 200 is high, the conductive band energy barrier between the conductive band energy barrier height of the second electron blocking layer 220 and the conductive band energy barrier height of the active layer 130 The height difference ΔE _c is larger, and the greater the effective conduction barrier height difference ΔE _c makes it less likely for electrons from the active layer 130 to overflow to the P-type semiconductor layer 120 . In the embodiment of FIG. 1 , the conductive band energy barrier formed by the second electron blocking layer 220 is 0.2 to 1 eV higher than the conductive band energy barrier formed by the active layer 130, so the effective conductive band energy barrier height difference ΔE _c It is 0.2 to 1 eV, which can effectively prevent the overflow of electrons from the active layer 130 to the P-type semiconductor layer 120, so as to effectively avoid the reduction of luminous efficiency caused by the overflow of electrons.

FIG. 6 is a schematic cross-sectional view of a UV-C light-emitting diode according to another embodiment of the present disclosure. 7 is a composition distribution diagram obtained by measuring a UV-C light-emitting diode of a comparative example by a secondary ion mass spectrometer, and FIG. 8 is a spectrum diagram of the UV-C light-emitting diode of a comparative example in FIG. 7 . Please refer to FIG. 6 first. The UV-C light-emitting diode 100 a of this embodiment is similar to the UV-C light-emitting diode 100 in FIG. 1 , and the differences between the two are as follows. In the UV-C light emitting diode 100 a of the present embodiment, the second electron blocking layer 220 of the electron blocking layer 200 a is located between the first electron blocking layer 210 and the active layer 130 . In this embodiment, the thickness T2a of the second electron blocking layer 220 falls within the range of 0.1 nm to 10 nm, while the thickness T1 of the first electron blocking layer 210 falls within the range of 10 nm to 100 nm. within range.

Please refer to FIG. 7 and FIG. 8 again. In this comparative example, it can be seen from FIG. Magnesium ions easily diffuse into the active layer 130 in a gradient distribution manner, causing defects to emit light, and a relatively obvious second luminescence peak P2 appears in the spectrum diagram of FIG. 8 . In this way, the luminous intensity of the UV-C light-emitting diode 100a of the comparative example becomes 5.4 mW. In order to reduce the situation that magnesium ions in the second electron blocking layer diffuse into the active layer 130 and cause defects to emit light, in another embodiment of the present disclosure, The electron blocking layer 200 can be made to have a magnesium concentration distribution as shown in FIG. Comparing the magnesium concentration in the active layer 130 in Fig. 7 and Fig. 9), it can be found that this kind of magnesium concentration distribution will not cause defects to emit light, and the corresponding spectrum (as shown in Fig. 10) in the first The secondary luminescence peak P2 is effectively suppressed and not obvious, and can hardly be seen. That is to say, this embodiment successfully makes the luminous intensity of the first luminous peak P1 greater than 20 times the defect luminous intensity of the second luminous peak P2.

FIG. 11 is a schematic cross-sectional view of a UV-C light-emitting diode according to another embodiment of the present disclosure. Please refer to FIG. 11 , the UV-C light-emitting diode 100 b of this embodiment is similar to the UV-C light-emitting diode 100 in FIG. 1 , and the differences between the two are as follows. In the UV-C light emitting diode 100b of this embodiment, the second electron blocking layer 220 of the electron blocking layer 200b is located in the first electron blocking layer 210 . In this embodiment, the thickness T2b of the second electron blocking layer 220 falls within the range of 0.1 nm to 15 nm, and the thickness of the first electron blocking layer 210 (that is, the thickness T11 in FIG. 11 plus the thickness T12) falls within the range of 10 nm to 100 nm.

FIG. 12 is a schematic cross-sectional view of a UV-C light-emitting diode according to yet another embodiment of the present disclosure. Please refer to FIG. 12 , the UV-C light-emitting diode 100 c of this embodiment is similar to the UV-C light-emitting diode 100 in FIG. 1 , and the differences between the two are as follows. In the electron blocking layer 200c of the UV-C light emitting diode 100c of this embodiment, the first electron blocking layer 210c has a superlattice structure. Specifically, the first electron blocking layer 210c has a plurality of first sublayers 212 and a plurality of second sublayers stacked alternately. Two sub-layers 214 , and both the first sub-layer 212 and the second sub-layer 214 are AlGaN layers doped with magnesium, but the aluminum concentration in the first sub-layer 212 is different from that in the second sub-layer 214 . That is to say, the concentration of aluminum in the first electron blocking layer 210 c is alternately high and low from the side close to the active layer 130 to the side close to the P-type semiconductor layer 120 .

In contrast, in the embodiments of FIG. 2 , FIG. 7 and FIG. 9 , the aluminum concentration of the first electron blocking layer 210 near the P-type semiconductor layer 120 is smaller than the aluminum concentration near the active layer 130 , for example, the first The aluminum concentration of the electron blocking layer 210 gradually increases from the side close to the P-type semiconductor layer 120 to the direction close to the active layer 130, and the difference between the aluminum concentration near the P-type semiconductor layer 120 and the aluminum concentration near the active layer 130 is about 5%. Cation mole fraction. The gallium concentration of the first electron blocking layer 210 near the P-type semiconductor layer 120 is greater than the gallium concentration near the active layer 130, and the difference between the gallium concentration near the P-type semiconductor layer 120 and the gallium concentration near the active layer 130 is about 5. % Cationic mole fraction.

In addition, in the embodiment of FIG. 12 , the second electron blocking layer 220 can also be disposed between the first electron blocking layer 210c and the active layer 130 , or disposed in the first electron blocking layer 210c.

FIG. 13 is a schematic cross-sectional view of a UV-C light-emitting diode according to another embodiment of the present disclosure. Please refer to FIG. 13 , the UV-C light-emitting diode 100d of this embodiment is similar to the UV-C light-emitting diode 100a of FIG. 6 , and the main differences between the two are as follows. In this embodiment, the UV-C light emitting diode 100d further includes a two-dimensional hole gas inducing layer 140 disposed between the active layer 130 and the P-type semiconductor layer 120d. The electron blocking layer 200d is disposed between the P-type semiconductor layer 120d and the two-dimensional hole gas inducing layer 140 . The material of the two-dimensional hole gas inducing layer 140 includes Al _α Ga _β N, wherein β=1-α, and 0.7<α≦0.95, wherein α is the cation mole fraction of aluminum in the compound Al _α Ga _β N (cationic molar fraction), and β is the cation molar fraction of gallium in the compound Al _α Ga _β N. The concentration of magnesium in the two-dimensional hole gas inducing layer 140 is less than 10 ¹⁷ atoms/cm3. In one embodiment, the concentration of magnesium in the active layer 130 is less than 10 ¹⁷ atoms/cm3. The material of the electron blocking layer 200d includes AlγGaδN, wherein _δ =1- _γ , and 0.65<γ≦0.9, wherein _γ is the cation mole fraction of aluminum in the compound AlγGaδN, and _δ is the compound Cationic mole fraction of _gallium in _AlγGaδN .

The concentration of magnesium in the portion of the electron blocking layer 200d adjacent to the two-dimensional hole gas inducing layer 140 is greater than 10 ¹⁹ atoms/cm 3 , or in one embodiment, greater than 10 ²⁰ atoms/cm 3 . The ultraviolet C light-emitting diode 100d satisfies α>γ and 0.1<α-γ≦0.3. The aluminum concentration of the two-dimensional hole gas inducing layer 140 is greater than that of the electron blocking layer 200d. The aluminum concentration difference between the two-dimensional hole gas inducing layer 140 and the electron blocking layer 200d is induced at the interface between the two-dimensional hole gas inducing layer 140 and the electron blocking layer 200d by spontaneous polarization and piezoelectric polarization. Two-dimensional hole gas. The induction of the two-dimensional hole gas promotes the direct injection of holes into the active layer 130, so the light efficiency of the UV-C light-emitting diode 100d is effectively improved. By adopting the two-dimensional hole gas inducing layer 140, the light output power of the UV-C light-emitting diode 100d is increased by 56%. The light output power of the encapsulated LED is increased from 17 mW (without the 2D hole gas inducing layer 140 ) to 26 mW (with the 2D hole gas inducing layer 140 ).

In this embodiment, the electron blocking layer 200d includes a first electron blocking layer 210d and a second electron blocking layer 220d, wherein the second electron blocking layer 220d is disposed between the two-dimensional hole gas inducing layer 140 and the first electron blocking layer Between 210d. The concentration of magnesium in the second electron blocking layer 220d is greater than the concentration of magnesium in the first electron blocking layer 210d, and the concentration of magnesium in the second electron blocking layer 220d is greater than 10 ¹⁹ atoms/cm3, or in one embodiment Medium is greater than 10 ²⁰ atoms/cubic centimeter. That is to say, the second electron blocking layer 220d is a portion of the aforementioned electron blocking layer 200d adjacent to the two-dimensional hole gas inducing layer 140 .

In this embodiment, the two-dimensional hole gas inducing layer 140 is in contact with the one of the energy well layers 134 that is closest to the two-dimensional hole gas inducing layer 140 . In this embodiment, the thickness T4 of the two-dimensional hole gas inducing layer 140 falls within a range of 1 nm to 3 nm. In this embodiment, the ratio of the thickness T3 of the electron blocking layer 200d to the thickness T4 of the two-dimensional hole gas inducing layer 140 falls within a range from 6 to 20. In one embodiment, the thickness T4 of the two-dimensional hole gas inducing layer 140 is, for example, in the range of 1 nm to 3 nm, and the thickness T3 of the electron blocking layer 200d is, for example, in the range from 20 nm to 60 nm. in the nanometer range.

For the light emitted by the active layer 130, the transmittance of the two-dimensional hole gas inducing layer 140 may be greater than that of the electron blocking layer 200d. In this embodiment, for the light emitted by the active layer 130, the transmittance of the two-dimensional hole gas inducing layer 140 is greater than the transmittance of the N-type semiconductor layer 110, and the transmittance of the N-type semiconductor layer 110 Less than the light transmittance of the electron blocking layer 200d.

In addition, the refractive index of the two-dimensional hole gas inducing layer 140 may be smaller than that of the electron blocking layer 200d. The refractive index of the two-dimensional hole gas inducing layer 140 is smaller than that of the N-type semiconductor layer 110 . In addition, the resistivity of the two-dimensional hole gas inducing layer 140 can be With a resistivity greater than that of the electron blocking layer 200d. The resistivity of the two-dimensional hole gas inducing layer 140 may be greater than that of the N-type semiconductor layer 110 . In addition, the aluminum concentration of the two-dimensional hole gas inducing layer 140 may be greater than the aluminum concentration of the N-type semiconductor layer 110 . Furthermore, the gallium concentration of the two-dimensional hole-gas inducing layer 140 is smaller than the gallium concentration of the electron blocking layer 200 d and smaller than the gallium concentration of the n-type semiconductor layer 110 . In one embodiment, the aluminum concentration of the electron blocking layer 200 d is greater than or equal to the aluminum concentration of the energy well layer 134 . In one embodiment, the aluminum concentration of the electron blocking layer 200 d is greater than or equal to the aluminum concentration of the energy barrier layer 132 .

In this embodiment, the P-type semiconductor layer 120d includes an aluminum graded layer 122d and a P-type semiconductor sub-layer 124d, wherein the P-type semiconductor sub-layer 124d is, for example, a magnesium-doped gallium nitride layer, and the aluminum graded layer 122d is, for example, is a Mg-doped AlGaN layer, wherein the Al concentration of the Mg-doped AlGaN layer decreases from the side close to the electron blocking layer 200d to the side close to the P-type semiconductor sub-layer 124d.

FIG. 14 is a composition distribution diagram obtained by measuring the ultraviolet C light-emitting diode in FIG. 13 by using a secondary ion mass spectrometer. The unit "c/s" in Fig. 14 means counts per second. Please refer to FIG. 13 and FIG. 14 , in the embodiment of FIG. 14 , the α of Al _α Ga _β N of the two-dimensional hole gas inducing layer 140 is, for example, 0.95. The magnesium concentration of the two-dimensional hole gas inducing layer 140 is less than 10 ¹⁷ atoms/cm3, and the magnesium concentration in the portion of the electron blocking layer 200d adjacent to the two-dimensional hole gas inducing layer 140 is about 10 ¹⁹ atoms/cm3 . The aluminum strength of the two-dimensional hole gas inducing layer 140 is greater than that of the electron blocking layer 200d, which means that the aluminum concentration of the two-dimensional hole gas inducing layer 140 is greater than that of the electron blocking layer 200d. The aluminum strength of the electron blocking layer 200 d is greater than that of the active layer 130 , which means that the aluminum concentration of the electron blocking layer 200 d is greater than that of the active layer 130 , including the aluminum concentrations of the energy well layer 134 and the energy barrier layer 132 . The aluminum intensity of the two-dimensional hole gas induction layer 140 is greater than that of the N-type semiconductor layer 110 , which means that the aluminum concentration of the two-dimensional hole gas induction layer 140 is greater than that of the N-type semiconductor layer 110 . The gallium intensity of the two-dimensional hole gas inducing layer 140 is smaller than the gallium intensity of the electron blocking layer 200d, and smaller than the gallium intensity of the N-type semiconductor layer 110. The gallium concentration of the two-dimensional hole gas inducing layer 140 is smaller than the gallium concentration of the electron blocking layer 200 d and smaller than the gallium concentration of the N-type semiconductor layer 110 .

FIG. 15 is an energy band diagram of the UV-C light-emitting diode in FIG. 13 . Please refer to FIG. 13 and FIG. 15. The physical meaning and unit “eV” of the curves corresponding to E _c , Ef _n , E _v and Ef _p in FIG. 15 are described in the paragraph explaining FIG. 5 and will not be repeated here. In addition, the curve corresponding to p in FIG. 15 and having the unit “cm ⁻³ ” refers to the hole density. It can be known from FIG. 15 that the two-dimensional hole gas inducing layer 140 induces the two-dimensional hole gas, so holes are generated in the two-dimensional hole gas inducing layer 140 . Therefore, the curve p has a peak corresponding to a high hole density inside the two-dimensional hole gas inducing layer 140 . Therefore, holes from the two-dimensional hole gas inducing layer 140 are injected into the active layer 130 . Therefore, the light efficiency of the UV-C LED 100d is effectively improved. By adopting the two-dimensional hole gas inducing layer 140, it can be known from the bandgap structure simulation that the extra electric current of the UV-C light-emitting diode 100d is 35 A/cm2. The hole carrier injection efficiency is increased from 10% (without the two-dimensional hole gas inducing layer 140 ) to 30% (with the two-dimensional hole gas inducing layer 140 ).

FIG. 16A is a graph showing the carrier injection efficiency of the UV-C light-emitting diode in FIG. 13 relative to α-γ when the magnesium concentration of the electron blocking layer is 10 ¹⁹ atoms/cm3. FIG. 16B is a graph showing the carrier injection efficiency of the UV-C light-emitting diode in FIG. 13 relative to α-γ when the magnesium concentration of the electron blocking layer is 10 ²⁰ atoms/cm3. FIG. 16A and FIG. 16B are simulated at a current density of 35 A/cm2. FIG. 16A shows that when the electron blocking layer 200d has a magnesium concentration of 10 ¹⁹ atoms/cm3, two-dimensional hole gas is formed under the condition of 0.2≦α-γ≦0.3. When two-dimensional hole gas is formed, the carrier injection efficiency will increase. In FIG. 16A , the carrier injection efficiency of α-γ=0.2 is slightly higher than that of α-γ=0.1, which indicates that the two-dimensional hole gas starts to form when α-γ=0.2. The carrier injection efficiency of α-γ=0.3 is even higher than that of α-γ=0.2, which indicates that the phenomenon of two-dimensional hole gas becomes stronger. FIG. 16B shows that when the magnesium concentration of the electron blocking layer 200d is 10 ²⁰ atoms/cm3, the two-dimensional hole gas is formed under the condition of 0.1<α-γ≦0.3. The magnesium concentration of the electron blocking layer 200d in FIG. 16B is higher than that of the electron blocking layer 200d in FIG. 16A , and the increase in carrier injection efficiency of 0.2≦α-γ is even greater in FIG. 16B compared to FIG. 16A . obvious. The higher the magnesium concentration in the electron blocking layer, the more two-dimensional hole gas will be generated in the two-dimensional hole gas inducing layer 140 . In Fig. 16, the carrier injection efficiency of α-γ=0.2 is much higher than that of α-γ=0.1, which means that when 0.1<α-γ, the two-dimensional hole gas begins to form.

FIG. 17 is a transmission electron microscopy (TEM) image of the UV-C light-emitting diode shown in FIG. 13 . Please refer to FIG. 13 and FIG. 17 . It can be seen from FIG. 17 that the two-dimensional hole gas inducing layer 140 forms bright white lines, which represent high light transmittance. When the aluminum concentration in the two-dimensional hole gas inducing layer 140 is higher, the transmittance of the two-dimensional hole gas inducing layer 140 is higher for light with a wavelength of 230 nm to 280 nm. When the cations of aluminum in the N-type semiconductor layer 110 Mo When the fraction ratio changes from 49% to 60%, the transmittance of the N-type semiconductor layer 110 changes from 0% to 76.3% for light with a wavelength of 230 nm to 280 nm. In addition, the aluminum concentration of the two-dimensional hole gas induction layer 140 can be greater than the aluminum concentration of the N-type semiconductor layer 110, so the penetration of the two-dimensional hole gas induction layer 140 for light with a wavelength of 230 nm to 280 nm The rate can be greater than 76.3%. The light transmittance of the two-dimensional hole gas inducing layer 140 makes the two-dimensional hole gas inducing layer 140 less likely to absorb light from the active layer 130 .

Each film layer of the UV-C light-emitting diode in each embodiment of the present disclosure can be manufactured by metal organic chemical vapor deposition (metal organic chemical vapor deposition, MOCVD) process or other appropriate semiconductor process, which is in the field It is well known to those of ordinary skill and therefore will not be described in detail here.

To sum up, in the UV-C light-emitting diode of the embodiment of the present disclosure, since the concentration of magnesium in the second electron blocking layer is greater than that in the first electron blocking layer, and the second electron The concentration of magnesium in the barrier layer is greater than the design of 10 ¹⁸ atoms/cm3, so the magnesium doping through a specific proportional relationship (for example, the above-mentioned magnitude relationship and numerical range of the magnesium concentration, and for example in Figure 2 and Figure 9 Magnesium concentration distribution curve) can effectively suppress the overflow of electrons in the active layer to the P-type semiconductor layer, thereby improving the device performance of the UV-C light-emitting diode. The UV-C light-emitting diodes of the disclosed embodiments adopt a two-dimensional hole gas induction layer, and meet the requirements of α>γ and 0.1<α-γ≦0.3, so the two-dimensional hole gas is induced in the two-dimensional hole gas formed at the interface between the layer and the electron blocking layer. The induction of the two-dimensional hole gas promotes the direct injection of holes into the active layer 130, so the light efficiency of the UV-C light-emitting diode 100d is effectively improved.

Although the present disclosure has been disclosed above with embodiments, it is not intended to limit the present disclosure. Anyone with ordinary knowledge in the technical field may make some changes and modifications without departing from the spirit and scope of the present disclosure. The scope of protection of this disclosure should be defined by the scope of the appended patent application.

50: first electrode

60: Second electrode

100d: Ultraviolet C LED

110: N-type semiconductor layer

112: the first N-type aluminum gallium nitride layer

114: the second N-type aluminum gallium nitride layer

120d: P-type semiconductor layer

122d: Aluminum gradient layer

124d: P-type semiconductor sublayer

130: active layer

132: Barrier layer

134: energy well layer

140: Two-dimensional hole gas induced layer

160: sapphire substrate

170: Aluminum nitride template layer

180: buffer layer

190: Unintentionally doped AlGaN layer

200d: electron blocking layer

210d: the first electron blocking layer

220d: the second electron blocking layer

T3, T4: Thickness

Claims (20)

An ultraviolet C light-emitting diode, comprising: an N-type semiconductor layer; a P-type semiconductor layer; an active layer, configured between the N-type semiconductor layer and the P-type semiconductor layer, the spectrum emitted by the active layer The wavelength of the maximum peak falls within the range of 230 nm to 280 nm; a two-dimensional hole gas induction layer is arranged between the active layer and the P-type semiconductor layer, wherein the two-dimensional hole gas induction layer The material includes Al _α Ga _β N, β=1-α, and the concentration of magnesium in the two-dimensional hole gas inducing layer is less than 10 ¹⁷ atoms/cm3; and an electron blocking layer is arranged on the P-type semiconductor layer and the two-dimensional hole gas induction layer, wherein the material of the electron blocking layer includes Al _γ Ga _δ N, δ=1-γ, 0.65<γ≦0.9, and the electron blocking layer adjacent to the two-dimensional electric The concentration of magnesium in the portion of the hole gas inducing layer is greater than 10 ¹⁹ atoms/cm3, wherein, α>γ and 0.1<α-γ≦0.3, so that the two-dimensional hole gas inducing layer and the electron blocking layer Two-dimensional hole gas is formed at the interface between them. The UV-C light-emitting diode as claimed in item 1, wherein 0.7<α≦0.95. The UV-C light-emitting diode as claimed in item 1, wherein 0.2≦α-γ≦0.3. The UV-C light-emitting diode as claimed in claim 1, wherein the concentration of magnesium in the portion of the electron blocking layer adjacent to the two-dimensional hole gas inducing layer is greater than 10 ²⁰ atoms/cm3. The ultraviolet C light-emitting diode as described in Claim 1, wherein the active layer is a multiple quantum well layer, and the multiple quantum well layer includes multiple energy well layers and multiple energy barrier layers stacked alternately, and the The two-dimensional hole gas inducing layer contacts the one of the energy well layers closest to the two-dimensional hole gas inducing layer. The UV-C light-emitting diode as claimed in item 5, wherein the aluminum concentration of the electron blocking layer is greater than or equal to the aluminum concentration of the energy well layers. The ultraviolet C light-emitting diode as claimed in item 5, wherein the aluminum concentration of the electron blocking layer is greater than or equal to the aluminum concentration of the energy barrier layers. The UV-C light-emitting diode as claimed in claim 1, wherein the thickness of the two-dimensional hole gas inducing layer falls within a range from 1 nm to 3 nm. The UV-C light-emitting diode as claimed in claim 1, wherein the ratio of the thickness of the electron blocking layer to the thickness of the two-dimensional hole gas inducing layer is in the range of 6-20. The UV-C light-emitting diode as claimed in claim 1, wherein for the light emitted by the active layer, the transmittance of the two-dimensional hole gas inducing layer is greater than that of the electron blocking layer. The ultraviolet C light-emitting diode as claimed in claim 10, wherein for the light emitted by the active layer, the transmittance of the two-dimensional hole gas induction layer is greater than the N The light transmittance of the N-type semiconductor layer, and the light transmittance of the N-type semiconductor layer is smaller than the light transmittance of the electron blocking layer. The UV-C light-emitting diode as claimed in claim 10, wherein the transmittance of the two-dimensional hole gas inducing layer is greater than 76.3% for the light emitted by the active layer. The UV-C light-emitting diode as claimed in claim 1, wherein the refractive index of the two-dimensional hole gas inducing layer is smaller than that of the electron blocking layer. The UV-C light-emitting diode as claimed in claim 1, wherein the refractive index of the two-dimensional hole gas inducing layer is smaller than that of the N-type semiconductor layer. The UV-C light-emitting diode as claimed in claim 1, wherein the resistivity of the two-dimensional hole gas inducing layer is greater than the resistivity of the electron blocking layer. The ultraviolet C light-emitting diode as claimed in claim 1, wherein the aluminum concentration of the two-dimensional hole gas induction layer is greater than the aluminum concentration of the N-type semiconductor layer. The ultraviolet C light-emitting diode as claimed in claim 1, wherein the gallium concentration of the two-dimensional hole gas induction layer is smaller than the gallium concentration of the electron blocking layer, and is smaller than the gallium concentration of the N-type semiconductor layer. The UV-C light-emitting diode as claimed in claim 1, wherein the electron blocking layer includes: a first electron blocking layer; and a second electron blocking layer disposed between the two-dimensional hole gas inducing layer and the second electron blocking layer Between an electron blocking layer, wherein the concentration of magnesium in the second electron blocking layer is greater than the concentration of magnesium in the first electron blocking layer, and the concentration of magnesium in the second electron blocking layer is greater than 10 ¹⁹ atoms/ Cubic centimeters. The UV-C light-emitting diode as claimed in claim 18, wherein the concentration of magnesium in the second electron blocking layer is greater than 10 ²⁰ atoms/cm3. The UV-C light-emitting diode as claimed in item 1, wherein the concentration of magnesium in the active layer is less than 10 ¹⁷ atoms/cm3.

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