WO2005106982A1 - Dispositif électroluminescent semi-conducteur de nitrure de groupe iii - Google Patents

Dispositif électroluminescent semi-conducteur de nitrure de groupe iii Download PDF

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WO2005106982A1
WO2005106982A1 PCT/JP2005/008552 JP2005008552W WO2005106982A1 WO 2005106982 A1 WO2005106982 A1 WO 2005106982A1 JP 2005008552 W JP2005008552 W JP 2005008552W WO 2005106982 A1 WO2005106982 A1 WO 2005106982A1
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layer
doped
group
nitride semiconductor
concentration
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PCT/JP2005/008552
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English (en)
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Hisayuki Miki
Akira Bando
Takashi Udagawa
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Showa Denko K.K.
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Publication of WO2005106982A1 publication Critical patent/WO2005106982A1/fr

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
    • H01L33/26—Materials of the light emitting region
    • H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
    • H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
    • H01L33/325—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen characterised by the doping materials

Definitions

  • This invention relates to a Group HI nitride semiconductor light-emitting device provided in the light-emitting layer thereof with a region doped with Ge.
  • the Group HI nitride semiconductors have been heretofore finding utility as a functional material for configuring Group HI nitride semiconductor light-emitting devices of the pn junction structure, such as light-emitting diodes (LEDs) and laser diodes (LDs), which emit a visible light of a short wavelength (refer, for example, to JP-A 2000-332364).
  • LEDs light-emitting diodes
  • LDs laser diodes
  • the light- emitting layers thereof generally have an n-type or a p-type Group HI nitride semiconductor layer joined thereto. These layers are intended to configure a light-emitting part in a hetero- junction structure with the object of acquiring emission of high intensity.
  • the contact layer which is intended to form an n-type electrode has been heretofore formed solely of a Group IH nitride semiconductor having silicon (Si) added thereto.
  • Si has been used also as a donor element for doping an active layer.
  • the so-called codoped configuration which uses an InGaN layer of a comparatively large film thickness for a light-emitting layer is doped with zinc (Zn) forming the center of emission and additionally doped with Si (refer, for example, to JP-A HEI 8-316528).
  • Zn zinc
  • Si silicon
  • n-type dopant in the GaN-based semiconductors generally germanium (Ge) and other elements have been known besides Si (refer, for example, to JP-A HEI 9-36423). These n-type dopants, however, are deficient in doping efficiency as compared with Si (refer, for example, to Jpn. J. Appl. Phys., 31 (9 A) (1992), 2883) and, therefore, are rated as disadvantageous for producing an n-type Group IH nitride semiconductor layer of low resistance.
  • the LED may be manufactured by having the light-emitting layer thereof kept undoped, i.e. not doped with a dopant. In this case, the omission of a doping treatment results in inevitably adding to the drive voltage.
  • the light-emitting layer is doped with an n-type dopant of some sort.
  • This invention is aimed at providing a Group HI nitride semiconductor light-emitting device including in a light-emitting layer thereof a region doped with Ge, namely a light- emitting device exhibiting excellent emission output without impairing the flatness of the light-emitting layer or inducing no loss of crystallinity.
  • the Group HI nitride semiconductor light-emitting device comprises a crystal substrate, an n-type and a p-type Group HI nitride semiconductor of
  • the region doped with Ge has a layer having an atomic concentration of Ge varied periodically.
  • the region doped with Ge is formed of a structure having a Group HI nitride semiconductor layer doped with Ge and a Group HI nitride semiconductor layer undoped therewith alternately stacked periodically.
  • the region doped with Ge comprises a Group HI nitride semiconductor layer doped with Ge to a higher concentration and a Group HI nitride semiconductor layer doped with Ge to a lower concentration, and the higher- concentration layer has a smaller thickness than the lower-concentration layer.
  • the Group HI nitride semiconductor layer doped with Ge to a lower concentration has surface flatness of 10 A or more.
  • the light-emitting layer including the region doped with Ge has a concentration of Ge atoms of 1 x 10 17 cm “3 or more and 1 x 10 2 cm " or iess.
  • the Group IH nitride semiconductor layer doped with Ge has a concentration of Ge atoms of 5 x 10 17 cm "3 or more and 5 x 10 19 cm “3 or less.
  • the light-emitting layer including the region doped with Ge has a multiple quantum well structure.
  • the region doped with Ge in the light-emitting layer is a barrier layer of multiple quantum well structure.
  • Fig. 1 is a schematic cross section illustrating the configuration of a stacked structure described in Example 1.
  • Fig. 2 is a schematic plan view of the LED described in Example 1.
  • Fig. 3 is a schematic cross section illustrating the configuration of a stacked structure described in Example 2.
  • Fig. 4 is a schematic plan view of the LED descried in Example 2.
  • Fig. 5 is a cross section depicting an artist's concept of the layer structure resulting from filling the pits occurring in a Ge high concentration layer with a Ge low concentration layer.
  • Fig. 6 is a schematic cross section illustrating the configuration of a stacked structure described in Comparative Example 1.
  • the inventors' experiment has yielded a result indicating that when Ge is used as a dopant for a light-emitting layer, the phenomenon that the emission output and the peak reverse voltage of the LED are degraded by aging does not appear.
  • Group IN elements such as Si and Ge, exhibiting n-type conductivity, when doped, are thought to be substituted for a Group HI element in the crystal to secure their existence.
  • Gallium nitride for example, is substituted for Ge.
  • Ge has an atomic radius larger than Si which is generally used as a dopant and nearly equal to Ga.
  • the stacked structure formed of a Group HE nitride semiconductor layers and constituting a light-emitting device which possesses a light-emitting layer including a region doped with germanium according to this invention is configured on a substrate which is made of sapphire ( ⁇ -Al 2 O 3 single crystal) having a relatively high melting point and having thermal resistance, an oxide single crystal material (such as zinc oxide (ZnO) or gallium lithium oxide (GaLiO 2 )), silicon (Si) single crystal or a Group IN semiconductor single crystal (such as cubic or hexagonal silicon carbide (SiC)).
  • sapphire ⁇ -Al 2 O 3 single crystal
  • an oxide single crystal material such as zinc oxide (ZnO) or gallium lithium oxide (GaLiO 2 )
  • silicon (Si) single crystal or a Group IN semiconductor single crystal such as cubic or hexagonal silicon carbide (SiC)
  • Group ⁇ i-N compound semiconductor single crystal material such as gallium phosphide (GaP) or gallium arsenide (GaAs) may be also usable.
  • GaP gallium phosphide
  • GaAs gallium arsenide
  • a single crystal substrate which is formed of gallium nitride crystal is included in the group of substrates which are available here.
  • An optically transparent single crystal material which is capable of passing the emission from a light-emitting layer can be effectively utilized as a substrate.
  • the lattice-unmatchable crystal epitaxial growth technique called a seeding process (SP) disclosed in JP-A 2003-243302 can be used.
  • SP seeding process
  • the SP process which manufactures an A1N crystal film at a high temperature enough to permit manufacture of a GaN-based crystal serves as a lattice- unmatchable crystal epitaxial growth technique which is excellent from the viewpoint of exalting productivity.
  • the gallium nitride-based semiconductor to be laid as the base is preferred to be GaN which is left undoped or doped meagerly to about 5 x 10 17 cm "3 .
  • the film thickness of the base layer is preferably in the range of 1 to 20 ⁇ m and more preferably in the range of 5 to 15 ⁇ m.
  • the Group HI nitride semiconductor light-emitting device possessing an active layer including a region doped with germanium atom according to this invention can be formed by means of gas phase growth, such as the metal organic chemical vapor deposition method (abbreviated as "MOCND,” “MONPE,” or “OMNPE”), the molecular beam epitaxial (MBE) method, the halogen gas phase growth method, and the hydride gas phase growth method.
  • MOCND metal organic chemical vapor deposition method
  • MBE molecular beam epitaxial
  • organic germanium compounds such as german gas (GeHi), tetramethyl germanium ((CH 3 ) 4 Ge) and tetraethyl germanium ((C 2 H5) 4 Ge), can be used.
  • the MBE method can use germanium in the elemental force as the source for doping.
  • the MOCND method for example, forms an n-type gallium nitride layer on the substrate of sapphire by using (CH 3 ) 4 Ge.
  • the active layer to be doped with Ge may be formed as a single layer of a thick film of 50 nm or formed in a quantum well structure.
  • the multiple quantum well structure When it is formed in the quantum well structure, it may be in the single quantum well structure having only one well layer or in the multiple quantum well structure having a plurality of well layers.
  • the multiple quantum well structure is used advantageously for the device using a Group HI gallium nitride-based compound semiconductor because it is enabled to combine high output and low drive voltage.
  • the total of the well layer (active layer) and the barrier layer will be referred to as a "light- emitting layer" in the present specification.
  • the active layer When the active layer is to be doped with Ge, the active layer may have the total volume thereof doped with Ge or it may have part of the region thereof doped with Ge.
  • the case of doping only the well layer the case of doping only the barrier layer, or the case of doping both of the layers is conceivable.
  • the case of doping the barrier layer proves particularly advantageous because this doping can lower the drive voltage without degrading the output of emission.
  • the doping effected only in part of the region in the barrier layer proves effective. In the case of forming the barrier layer in the region growing at a high temperature and the region growing at a low temperature, for example, the doping effected in the region growing at the low temperature can be expected to bring a more prominent decline of the drive voltage.
  • the amounts of Ge doping given to the individual barrier layers do not need to be equalized.
  • the decrease in the concentration of Ge particularly in the barrier layer approximating closely to the region contiguous to the p-layer is effective in exalting the output and lowering the drive voltage. This exaltation of the output can be promoted particularly by keeping the barrier layer approximating most closely to the p-layer from undergoing a doping treatment.
  • the number of layers to be stacked is preferably in the range from three to ten and more preferably in the range from three to six.
  • the film thickness of the barrier layer is preferably 70 A or more and more preferably 140 A or more. I-f the film thickness of the barrier layer is unduly small, the shortage will result in obstructing the flattening of the upper surface of the barrier layer and inducing a decrease in the efficiency of emission and a decrease in the aging characteristics. If the film thickness is unduly large, the overage will result in inducing an increase in the drive voltage and a decrease in the emission.
  • the film thickness of the barrier layer is preferred to be 500 A or less.
  • the active layer is preferably formed of an In-containing gallium nitride-based compound semiconductor.
  • the In-containing gallium nitride-based compound semiconductor can emit light in a blue color wavelength region with high intensity.
  • the barrier layer can be formed of InGaN which has a smaller In ratio than the InGaN forming the well layer (active layer) besides GaN and AlGaN.
  • GaN proves particularly advantageous.
  • the region doped with Ge may be given a structure having the concentration of germanium atom periodically varied with the object of securing the flatness of the surface.
  • This region is formed by periodically varying with time during the gas phase growth of the Group HI nitride semiconductor layer the amount of the source for doping Ge to be supplied to the gas phase growth reaction system.
  • a thin layer containing Ge atom in a high concentration is formed, for example, by instantaneously supplying a large amount of the source for doping Ge to the gas phase growth region after a thin undoped layer has been formed without supplying the source for doping Ge to the gas phase growth region.
  • This formation may be otherwise attained by growing the thin layer having a low concentration of Ge atom and subsequently suspending the growth till the conditions for growth such as the V/IH ratio are adjusted to suit the addition of Ge atom to a high concentration, thereby enabling a thin layer containing Ge atom in a high concentration to be joined thereto.
  • the Group HI nitride semiconductor layer doped with Ge to a high concentration and used in the technique proposed by this invention (Ge atom high concentration layer), when it uses Ge as a dopant, inherently has such a high concentration as to produce pits in the surface thereof.
  • the surface on the high concentration layer side (the opposite side from the substrate) contains pits of a convex shape while the surface on the low concentration layer side (the opposite side from the substrate) assumes a flat surface.
  • the cross section depicting an artist's concept of the layer structure resulting from filling the pits occurring in a Ge atom high concentration layer with a Ge atom low concentration layer is shown in Fig.
  • 4a denotes a Ge atom high concentration layer
  • 4c denotes pits
  • 4b denotes a Ge atom low concentration layer.
  • the surface of the low concentration layer 4b is flattened in consequence of filling the pits 4c occurring in the surface of the high concentration layer 4a with the low concentration layer 4b.
  • the pits occurring in the Ge atom high concentration layer of this invention are considered to occur at the positions of the so-called threading dislocation originating from the interface between the substrate and the Group HI nitride semiconductor layer. More often than not, therefore, the density of the pits occurring in the high concentration layer approximately coincides with the density of the threading dislocation in the base.
  • the density of threading dislocation in the base falls in the range of 1 x 10 7 to 1 x 10 10 /cm 2 .
  • the products having a density of pits of 1 x 10 7 /cm 2 or less are not realized at present and the products having a density of pits of 1 x 10 10 /cm 2 or more, even when they are used in a substrate for an electron device, cannot show a fully satisfactory function.
  • the density of pits is in the range of 1 x 10 6 to 1 x 10 10 /cm 2 , though depending on the density of threading dislocations in the base.
  • the high concentration layer alone is manufactured in a film thickness of about 10 nm or more, these pits can be observed by using such means as an atomic force microscope (AFM).
  • AFM atomic force microscope
  • the film thickness is increased to about 500 nm, they can be observed by the use of an optical microscope.
  • these pits may possibly become invisible because of the resolution of the atomic force microscope.
  • this thickness is increased to a certain extent and the film-forming conditions are adjusted to permit observation of the pits, the pits are thought to have occurred in spite of a very small thickness falling short of 10 nm.
  • the surface of the Ge atom low concentration layer of this invention is preferred to be flat.
  • the flatness of the surface is preferred to be approximately 10 A or less and more preferably to be 5 A or more in the Ra value.
  • the total layer thickness of the region having the concentration of Ge atom periodically varied is properly 5 nm or more and 100 nm or less. It is preferably 10 nm or more and 70 nm or less and more preferably 15 nm or more and 50 nm or less. If this layer thickness falls short of 5 nm, the shortage will result in adding to the conspicuousness of the deterioration of the well layer by aging. If it exceeds 100 nm, the overage will result in inducing degradation of the emission output.
  • the total of the film thickness of the n-type Group HI nitride semiconductor layer containing Ge in a high concentration and the film thickness of the n-type nitride semiconductor layer containing Ge in a low concentration, namely the periodic film thickness, is properly 0.5 nm or more, preferably 1 nm or more and more preferably 2 nm or more. If the total of the film thickness falls short of 0.5 nm, the shortage will render it difficult to obtain the effect of periodically stacking the Ge doped layers. Specifically, when the layer doped with Ge to a high concentration is thicker than the layer doped with Ge to a low concentration in one period, the occurrence of pits cannot be repressed and the flatness cannot be easily obtained.
  • the thickness of the layer doped with Ge to a low concentration is equal to or greater than the thickness of the layer doped with Ge to a high concentration, the flatness is good.
  • the thickness of the layer doped with Ge to a low concentration therefore, is preferred to have a greater layer thickness than the thin layer doped with Ge.
  • the low concentration layer is unduly large, this overage will prove unfavorable for obtaining a Group HI nitride semiconductor light-emitting device having a low forward voltage (so-called Nf) or threshold voltage (so-called, Nth).
  • the number of periodically stacked layer is suitably 1 or more and 200 or less, preferably 1 or more and 100 or less, and more preferably 1 or more and 50 or less.
  • the concentration of Ge atoms in the interior of the n-type Group HI nitride semiconductor layer containing Ge at a high concentration is suitably 1 x 10 17 cm “3 or more and 1 x 10 cm “ or less, preferably 5 x 10 cm “ or more and 5 x 10 cm “ or less, and more preferably 3 x 10 18 cm “3 or more and 2 x 10 19 cm “3 or less.
  • the concentration of Ge atoms in the interior of the n-type Group HI nitride semiconductor layer containing Ge at a high concentration does not need to be fixed but may be varied continuously or discontinuously.
  • the concentration of Ge atom in the interior of the n-type Group HI nitride semiconductor layer containing Ge at a low concentration is lower than the concentration of Ge atom in the interior of the n-type Group HI nitride semiconductor layer containing Ge at a high concentration and is suitably the lower limit of determination or more by the following analytical method and 2 x 10 19 cm “3 or less, preferably the lower limit of determination or more and 1 x 10 19 cm “3 or less and more preferably the lower limit of determination or more and 5 x 10 18 cm “3 or less. It is rather preferable to leave out the doping treatment.
  • the concentration of Ge atom in the interior of the n-type Group HI nitride semiconductor layer containing Ge at a low concentration does not need to be fixed but may be varied continuously or discontinuously. If the concentration of Ge atom is suffered to exceed 2 x 10 19 cm 3 , the excess will be at a disadvantage in sharply increasing the density of pits in the surface.
  • the concentration of Ge atom can be determined, for example, by the method of secondary ion mass spectroscopy (abbreviated as "SIMS"). This method comprises irradiating the surface of a sample with a primary ion and analyzing the mass of an element expelled consequently in an ionized state and permits observation and determination of the distribution of concentration of a specific element in the direction of depth.
  • SIMS secondary ion mass spectroscopy
  • This method is effective with respect to the Ge element which is present in the Group HI nitride semiconductor layer.
  • the increase of the concentration of Ge atom in a layer doped with Ge to a high concentration above 5 x 10 17 cm “3 can contribute to the configuration of an LED having a low forward voltage.
  • the concentration is 5 x 10 19 cm “3
  • the total carrier concentration in the region having the concentration of Ge atom periodically varied is approximately (3 to 4) x 10 19 cm “3 . If the doping with Ge is performed in excess of this atomic concentration, the excess will be at a disadvantage in sharply increasing the density of pits in the surface.
  • the composition may be changed between a region doped with Ge to a high concentration and a region doped with Ge to a low concentration.
  • the inclusion of In and Al in the composition of a layer doped with Ge constitutes an important technique for realizing the flattening of the surface.
  • the concentration of In so included therein is preferably 0.1 atom% or more and 50 atom% or less and optimally 1 atom% or more and 20 atom% or less.
  • the concentration of Al so included therein is preferably 0.1 atom% or more and 20 atom% or less and optimally 0.5 atom% or more and 10 atom% or less.
  • an n-clad layer is interposed between the contact layer and the light- emitting layer.
  • the n-clad layer may be formed of AlGaN, GaN or InGaN.
  • the n-clad layer is preferred to have a larger composition than the band gap of InGaN in the active layer.
  • the carrier concentration in the n-clad layer may be equal to the n-contact layer or may be larger or smaller than that.
  • the n-clad layer may be formed by having two layers differing in composition and lattice constant alternately stacked a plurality of times.
  • the two layers may be made to differ in the amount of dopant and the film thickness besides the composition.
  • the p-type layer generally has a thickness in the range of 0.01 to 1 ⁇ m and is composed of a p-clad layer which is held in contact with the active layer and a p-contact layer which is intended to form a positive electrode.
  • the p-clad layer and the p-contact layer may serve in the place of each other.
  • the p-clad layer is formed using GaN or AlGaN, for example, and is doped with Mg as a p-dopant.
  • the outermost surface is preferably formed as a layer of a high carrier concentration while most layers may possess high resistance. That is, the amount of the dopant may be safely decreased and the inclusion of hydrogen, a substance which is held to obstruct the activation of the dopant, may be safely tolerated. These actions are rather at an advantage in enhancing the reverse blocking voltage for a configured device.
  • the p-clad layer may likewise be formed by having two layers differing in composition and lattice constant alternately stacked a plurality of times. Depending on the layers to be stacked, in this case, the two layers may be made to differ in the amount of dopant and the film thickness besides the composition.
  • the p-contact layer may be made of GaN, AlGaN or InGaN, for example, and may be doped with Mg as an impurity.
  • the gallium nitride-based compound semiconductor doped with Mg generally possesses high resistance while still fresh from the reaction furnace. It is held to exhibit p-conductivity after undergoing activating treatments, such as the annealing treatment, the treatment of irradiation with an electron beam and the treatment of irradiation with a microwave. As already stated, it may be put to use without undergoing the aforementioned activating treatment.
  • the p-contact layer which is formed of boron phosphide doped with a p-type impurity may be used.
  • the boron phosphide doped with p-type impurity exhibits p- conductivity even when it is not subjected to the aforementioned treatment for the conversion to the p-type.
  • the method for growing the gallium nitride-based compound semiconductor of which the n-type layer, the active layer and the p-type layer are formed does not need to be particularly restricted.
  • the well-known methods such as MBE, MOCND, and HNPE may be used under well-known conditions.
  • the MOCND method proves particularly favorable.
  • the raw materials for the source of nitrogen ammonia, hydrazine and azides may be used.
  • TMGa trimethyl gallium
  • TMGa triethyl gallium
  • TIn trimethyl indium
  • TMAl trimethyl aluminum
  • sources for dopant silane, disilane, german, organic germanium raw materials and biscyclopentadienyl magnesium (Cp 2 Mg) may be used.
  • carrier gas nitrogen and hydrogen may be used.
  • the growth of an active layer containing In is preferably carried out with the substrate temperature kept in the range of 650 to 900°C. If the temperature falls short of the lower limit of this range, the shortage will not allow production of an active layer of satisfactory crystallinity.
  • the overage will possibly result in decreasing the amount of In to be incorporated in the active layer and preventing the device emitting light of an intended wavelength from being manufactured.
  • the growth of part of the region of the barrier layer is preferably carried out at a higher substrate temperature than the growth of the well layer (active layer).
  • the higher substrate temperature is preferred to be in the range of 700 to 1,000°C.
  • the negative electrodes are known in various compositions and various structures. These well-known negative electrodes may be used without any restriction.
  • the contacting materials to be used for the negative electrodes which are destined to contact the n-contact layer not only Al, Ti, ⁇ i and Au but also Cr, W and N may be used.
  • the impartation of the bonding property to the negative electrode is accomplished by configuring the negative electrode wholly in a multilayer structure.
  • the coating of the outermost surface of the negative electrode with Au is at an advantage in facilitating the bonding.
  • the positive electrodes are also well known in various compositions and structures. These well-known positive electrodes may be used without any restriction.
  • the positive layer materials pervious to light may include Pt, Pd, Au, Cr, Ni, Cu and
  • the positive electrodes are enabled to acquire enhanced perviousness to light by having them configured in a partly oxidized structure.
  • As reflecting positive electrode materials Rh, Ag, Al, for example, may be used besides the aforementioned materials.
  • These positive electrodes may be configures by methods, such as sputtering and vacuum evaporation. Particularly when the sputtering is adopted, the positive electrodes are enabled by properly controlling the conditions of sputtering to acquire ohmic contact without undergoing an annealing treatment after the formation of an electrode film. Thus, the sputtering proves favorable.
  • the light-emitting device may be configured in a flip-chip structure which is provided with a reflecting positive electrode or in a face-up structure which is provided with a light-pervious positive electrode or a lattice or comb positive electrode.
  • Example 1 First, this invention will be specifically described citing as an example the case of configuring a Group HI nitride semiconductor light-emitting diode by stacking a light- emitting layer furnished with a Ge-doped barrier layer and formed of a multiple quantum well on a Ge-doped GaN layer stacked, with the concentration periodically varied.
  • the dopant concentrations reported in the description were invariably determined by the SIMS method described above.
  • the film thicknesses were determined by a method using a reflectance spectrum of a white light and by the observation of a cross section transmission electron microscope (TEM). These determinations apply to Example 2 and the subsequent examples. ' Fig.
  • FIG. 1 schematically illustrates the profile of an epitaxially stacked structure for the manufacture of an LED described in the present example.
  • the schematic section of an LED chips manufactured in the present example is illustrated in Fig. 2.
  • the epitaxially stacked structure was configured by the following procedure using a common reduced-pressure MOCND means.
  • a (OOOl)-sapphire substrate 101 was mounted on a susceptor made of a semiconductor-grade, high-purity graphite and adapted to be heated by a radio-frequency (RF) induction heater to a film-forming temperature.
  • RF radio-frequency
  • the induction heater was set operating to elevate the temperature of the substrate 101 from room temperature to 600°C over a period of 10 minutes. While the temperature of the substrate 101 was kept at 600°C, the pressure in the gas phase growth reaction furnace was increased by supply of hydrogen gas and nitrogen gas to 1.5 x 104 pascals (unit of pressure: Pa). The substrate 101 was left standing at the temperature under the pressure mentioned above for 2 minutes to effect thermal cleaning of the surface thereof. After the thermal cleaning was completed, the supply of the nitrogen gas to the interior of the gas phase growth reaction furnace was stopped. The supply of the hydrogen gas was continued. Thereafter, in the atmosphere of hydrogen, the temperature of the substrate 101 was elevated to 1,120°C.
  • the hydrogen gas entraining vapor of trimethyl aluminum (TMAl) was supplied for a period of 8 minutes and 30 seconds into the gas phase growth reaction furnace. Consequently, the trimethyl aluminum was made to react with the nitrogen ( ⁇ ) atom generated in consequence of the decomposition of the nitrogen ( ⁇ )-containing deposit formerly adhering to the inner wall of the gas phase growth reaction furnace and induce deposition of an aluminum nitride (AIN) thin film (not shown) having a thickness of several nm on the sapphire substrate 101.
  • TMAl trimethyl aluminum
  • the susceptor After the temperature of the susceptor was confirmed to have reached 1040°C, the susceptor was left standing for a while till the temperature thereof was stabilized and the supply of trimethyl gallium (TMGa) into the gas phase growth reaction furnace was started to induce the growth of an undoped GaN layer 102 over 4 hours.
  • the thickness of the undoped GaN layer 102 was 8 ⁇ m.
  • the temperature of the wafer was elevated to 1140°C and allowed to stabilize.
  • a cycle of continuing flow of tetramethyl germanium ((CH 3 ) Ge) and then stopping the flow was carried out up to 100 repetitions to form a Ge-doped GaN layer 103 measuring 2.0 ⁇ m in thickness and having a Ge concentration varied periodically.
  • Ge high concentration layer was observed under an atomic force microscope, the number of pits formed on the surface of the high concentration layer was found to be 2 x 10 7 /cm 3 .
  • a Ge-doped n-type Ino.o ⁇ Gao. 94 N clad layer 104 was stacked thereon. The thickness of this clad layer 104 was 12.5 nm and the amount of Ga doping was 1 x 10 18 cm "3 .
  • the temperature of the substrate 101 was set at 730°C and a multiple quantum well structure light-emitting layer 105 of a five-cycle structure comprising a barrier layer of GaN and a well layer of l o. 2 5Gao.
  • a Ge- doped GaN barrier layer was disposed as joined to a Ge-doped n-type l o.o 6 Gao. 94 N clad layer 104.
  • the GaN barrier layer was grown by using triethyl gallium (TEGa) as the source for gallium and tetraethyl germanium (TEGe) as the source of dopant.
  • TMGa triethyl gallium
  • TMGe tetraethyl germanium
  • TMGa triethyl gallium
  • TMIn trimethyl indium
  • Mg magnesium
  • Bis-cyclopentadienyl magnesium (bis-Cp 2 Mg) was used as the source for Mg doping.
  • the addition of Mg was so performed as to give the p-type GaN contact layer 107 a hole concentration of 8 x 10 17 cm '3'
  • the thickness of the p-type GaN contact layer 107 was 100 nm.
  • a stacked structure 11 was taken out of the gas phase growth reaction furnace.
  • the p-type GaN contact layer 107 was already showing p-type conductivity without undergoing an annealing treatment electrically activating the p-type carrier (Mg).
  • the surface of the GaN layer 103 doped with Ge to a high concentration was exposed exclusively in the region expected to form an n-type ohmic electrode 108 by using the known photolithographic technique and the common dry etching technique.
  • an n-type ohmic electrode 108 having chromium (Cr) and gold (Au) deposited on the surface side thereof was formed.
  • a reflection p-type ohmic electrode 109 having platinum (Pt), silver (Ag) and gold (Au) sequentially stacked thereon from the surface side was formed by using the common sputtering means and the known photolithographic means.
  • an LED chip 10 cut in a square of 350 ⁇ m as seen in a plan view was joined to a wire connection auxiliary member called a "submount.”
  • the LED chip on the submount was mounted on a lead frame (not shown) in order that a gold wire (not shown) connected to the lead frame may advance a device drive current from the lead frame to the LED chip 10.
  • the device drive current was advanced in the forward direction between the n-type and p-type ohmic electrodes 108 and 109.
  • the forward voltage was 3.0 N when the forward current was set at 20 mA. While the 20 mA forward current was flowing, the central wavelength of the blue band emission to be emitted was 460 nm.
  • the intensity of the emission determined by using the ordinary integrating sphere reached 12 mW.
  • the Group HI nitride semiconductor LED yielding emission of high intensity was completed.
  • the LED thus manufactured had a current of 50 mA conducted thereto for 1000 hours, it was subjected to the same determination as mentioned above. This determination found no change in the intensity of emission and in the drive voltage.
  • the peak reverse voltage for effecting conduction of 10 ⁇ A was not changed from 20 N.
  • Example 2 First, this invention will be described citing the case of configuring a Group HI nitride semiconductor light-emitting diode by causing a light-emitting layer 111 of a multiple quantum well structure having an undoped Ga ⁇ layer and a Ge-doped Ga ⁇ layer alternately stacked to be deposited as a barrier layer via an n-type clad layer 104 on a Ge- doped Ga ⁇ layer 103 stacked by periodically varying the concentration.
  • Fig. 2 schematically illustrates the profile in cross section of an epitaxially stacked structure 12 for the manufacture of an LED described in the present example. The manufacture up to the formation of the Ge-doped n-type Ino.o6Gao.
  • Example 1 The doping amount of Ge was set at 1 x 10 18 cm "3 and the thickness of the clad layer was set at 50 nm. Then, after the temperature of the substrate 101 was set at 730°C, a multiple quantum well structure light-emitting layer 111 of a 5 -cycle structure comprising a barrier layer formed by stacking an undoped GaN layer 2 nm in thickness and a Ge-doped GaN layer 2 nm in thickness each up to four cycles and a well layer formed of undoped Itio. 2 5Gao. 7 5N was disposed on a Ge-doped n-type Ino.o 2 Gao.
  • the GaN barrier layer was disposed as joined to the Ge-doped n-type In..o6Gao. 94 N clad layer 104.
  • the GaN barrier layer was grown by using triethyl gallium (TEGa) as the source for gallium and tetraethyl germanium (TEGe) as the source for germanium.
  • TSGa triethyl gallium
  • TMGe tetraethyl germanium
  • the total layer thickness was 16 nm. It was configured by stacking an undoped GaN layer 2 nm in thickness and a Ge-doped GaN layer 2 nm in thickness each up to four cycles.
  • the amount of Ge in the Ge-doped region was set at 1 x 10 18 cm "3 .
  • the Ino. 2 _Gao. 7 5N well layer was grown by using triethyl gallium (TEGa) as the source for gallium and trimethyl indium (TMJn) as the source for indium.
  • TSGa triethyl gallium
  • TMJn trimethyl indium
  • the layer had a thickness of 2.5 nm and was not doped.
  • the p-type contact layer 107 was stacked by following the procedure of Example 1 and the wafer was subsequently taken out of the reactor. Then, the surface of the GaN layer 103 doped with Ge to a high concentration was exposed exclusively in the region expected to form an n-type ohmic electrode 108 by using the known photolithographic technique and the common dry etching technique.
  • an n-type ohmic electrode 108 having titanium (Ti) and gold (Au) stacked on the surface side thereof was formed.
  • a transparent p-ohmic electrode 109 having platinum (Pt) and gold (Au) stacked sequentially from the front surface side and a bonding-grade electrode 110 were formed by using the common vacuum evaporation means and the known photolithographic means.
  • an LED chip 20 cut in a square of 350 ⁇ m as seen in a plan view was mounted on a lead frame (not shown) and a gold wire (not shown) was connected to the lead frame so as to allow conduction of the device drive current from the lead frame to the LED chip 20.
  • the device drive current was passed in the forward direction between the n-type and p-type ohmic electrodes 108 and 109.
  • the forward voltage was 2.9 V when the forward current was set at 20 mA.
  • the central wavelength of the blue band emission emitted during the flow of the forward current of 20 mA was 460 nm.
  • the intensity of the emission determined by using the ordinary integration sphere reached 5.5 mW.
  • Comparative Example 1 A Ge-doped Ga ⁇ layer 103 having a Ge concentration periodically varied was formed as an n-type contact layer in the same manner as in Example 1, and a multiple quantum well structure 112 of Ga ⁇ having a barrier layer thereof doped with Si in the place of Ge of Example 1 was stacked as a light-emitting layer. Thereafter, an LED was manufactured by forming electrodes, mounting them on a lead frame and making necessary connection under the same conditions as in Example 2 on the stacked structure 13 of Fig. 6 formed of a p-type Al 0 .o 7 Gao. 93 ⁇ clad layer 106 and a p-type GaN contact layer 107 under the same conditions as in Example 1.
  • the forward voltage was 2.9 V when the forward current was set at 20 mA.
  • the central wavelength of the blue band emission emitted during the conduction of the forward current of 20 mA was 460 nm.
  • the intensity of the emission determined by using the ordinary integration sphere was 4 mW, a magnitude lower than when an Si-doped GaN layer was used as a barrier layer.
  • the intensity of emission was found to have dropped to 3 mA.
  • the peak reverse voltage required for conduction of 10 ⁇ A fell from 20 V to 5 V.
  • the light-emitting device obtained by using a stacked gallium nitride-based compound semiconductor according to this invention shows no change of characteristic properties in consequence of aging due to a protracted conduction of electric current. Thus, it has an immense commercial value.

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Abstract

Il est prévu un dispositif électroluminescent semi-conducteur de nitrure de groupe III contenant un substrat de cristal, un semi-conducteur de type n et de type p de AlXGaYInZN1-aMa, où 0 ≤ X ≤ 1, 0 ≤ Y ≤ 1, 0 ≤ Z ≤ 1, X + Y + Z = 1, M dénote un élément de groupe V autre que N et 0 ≤ a < 1, formé sur le substrat de cristal, et une couche électroluminescente comprenant une région dopée au Ge.
PCT/JP2005/008552 2004-04-28 2005-04-28 Dispositif électroluminescent semi-conducteur de nitrure de groupe iii WO2005106982A1 (fr)

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2009707A2 (fr) * 2007-06-25 2008-12-31 Seoul Opto-Device Co., Ltd. Diode électroluminescente et son procédé de fabrication
WO2012035135A1 (fr) * 2010-09-19 2012-03-22 Osram Opto Semiconductors Gmbh Microplaquette semi-conductrice et procédé de production
CN109686823A (zh) * 2018-11-26 2019-04-26 华灿光电（浙江）有限公司 一种氮化镓基发光二极管外延片及其制作方法

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001102629A (ja) * 1999-09-28 2001-04-13 Nichia Chem Ind Ltd 窒化物半導体素子

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001102629A (ja) * 1999-09-28 2001-04-13 Nichia Chem Ind Ltd 窒化物半導体素子

Non-Patent Citations (1)

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Title
ZHANG X. ET AL: "Observation of room temperature surface-emitting stimulated emission from GaN:Ge by optical pumping.", J.APPL.PHYS., vol. 80, no. 11, 1996, XP002990892 *

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2009707A2 (fr) * 2007-06-25 2008-12-31 Seoul Opto-Device Co., Ltd. Diode électroluminescente et son procédé de fabrication
EP2009707A3 (fr) * 2007-06-25 2012-07-25 Seoul Opto Device Co., Ltd. Diode électroluminescente et son procédé de fabrication
WO2012035135A1 (fr) * 2010-09-19 2012-03-22 Osram Opto Semiconductors Gmbh Microplaquette semi-conductrice et procédé de production
CN109686823A (zh) * 2018-11-26 2019-04-26 华灿光电（浙江）有限公司 一种氮化镓基发光二极管外延片及其制作方法

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