JP2008282836A - Semiconductor laser device and manufacturing method of nitride semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a nitride semiconductor device, having small deterioration in the device characteristics, caused by an etching damage and small variation in device characteristics caused by variation in etching. <P>SOLUTION: The manufacturing method of a nitride semiconductor device has a step, in which a first nitride semiconductor layer 17 and a second nitride semiconductor layer 18 having a Fermi level larger than that of the first nitride semiconductor layer 17, as well as, containing an n-type impurity are formed on a substrate 11 sequentially from the substrate 11 side. In addition, the manufacturing method has a step, in which the second nitride semiconductor layer 18 is etched so that the etching is automatically stopped, in a state where the second nitride semiconductor layer 18 remains, by making the second nitride semiconductor layer 18 react with an alkali etchant, while irradiating the second nitride semiconductor layer 18 with a light. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a semiconductor laser device using a nitride semiconductor material and a method for manufacturing the semiconductor device.

Currently, gallium nitride (GaN) as a representative, in the group III element of the general formula expressed by the _{In X Ga Y Al 1-X} -Y N (0 ≦ X ≦ 1,0 ≦ Y ≦ 1, X + Y ≦ 1) A group III-V nitride-based compound semiconductor composed of a certain aluminum (Al), gallium (Ga), and indium (In) and nitrogen (N) which is a group V element, so-called nitride semiconductor, has attracted attention. In particular, it is expected as a material for electronic devices such as light-emitting diodes (LEDs), optical devices such as blue-violet semiconductor laser devices (LDs), and field effect transistors (FETs).

In order to manufacture a semiconductor device such as an optical device and an electronic device using a nitride semiconductor, a technique for processing the nitride semiconductor into an arbitrary shape is required. In order to form the current confinement structure of the LD and the gate recess of the FET, it is necessary to selectively etch the nitride semiconductor layer. Generally, dry etching is used for etching a nitride semiconductor (see, for example, Patent Document 1).
JP 2003-142780 A Appl. Phys. Lett, 72, 5, 1998, p. 560-562

  However, when the nitride semiconductor layer is etched by dry etching, there are the following problems.

  First, since dry etching is performed by causing ions to collide with a semiconductor layer, the semiconductor layer is greatly damaged. For this reason, when a recessed part is formed by dry etching, there exists a problem that the characteristic of a device deteriorates by the damage of etching.

  Also, dry etching is a technique with considerably good controllability. However, since variation of several percent occurs, for example, when an AlGaN layer formed on a GaN layer is removed, overetching or underetching is unavoidable. For this reason, there is a problem that device characteristics vary.

  For this reason, it is ideal that the etching method used for manufacturing the semiconductor device is small in damage caused by etching and self-stops at the interface between the two semiconductor layers.

  On the other hand, the inventors of the present application have found a wet etching condition that causes less damage and can self-stop etching in the vicinity of the interface between two semiconductor layers.

  The present application solves the above-mentioned conventional problems based on the knowledge of the inventors of the present application, and can realize a method for manufacturing a nitride semiconductor device in which device characteristic deterioration due to etching damage and device characteristic variation due to etching variation are small. The purpose is to.

  In order to achieve the above object, the present invention provides a method for manufacturing a semiconductor device comprising a step of etching an n-type semiconductor layer by photoelectrochemical etching.

  Specifically, in the method for manufacturing a nitride semiconductor device according to the present invention, a first nitride semiconductor layer and a Fermi level larger than the first nitride semiconductor layer and an n-type impurity are formed on a substrate. A step (a) of sequentially forming a second nitride semiconductor layer containing a second nitride semiconductor layer from the substrate side, and etching the second nitride semiconductor layer using photoelectrochemical etching to thereby form a second nitride semiconductor layer And the step (b) of selectively removing the second nitride semiconductor layer by self-stopping the etching in a state where the metal remains.

  According to the method for manufacturing a nitride semiconductor device of the present invention, the method includes the step of selectively removing the second nitride semiconductor layer by self-stopping the etching while the second nitride semiconductor layer remains. Therefore, only the upper layer of the two stacked nitride semiconductor layers can be selectively removed with good reproducibility. Therefore, variation in characteristics between semiconductor devices due to variation in etching can be suppressed, and a semiconductor device can be manufactured with high yield. Further, there is almost no damage to the etching layer, and deterioration of the characteristics of the semiconductor device due to the etching damage can be suppressed.

  In the method for manufacturing a semiconductor device of the present invention, the etching stop position in the step (b) can be controlled by the difference in Fermi level between the first nitride semiconductor layer and the second nitride semiconductor layer.

  In the semiconductor device manufacturing method of the present invention, the etching stop position in step (b) can be controlled by the carrier concentrations of the first nitride semiconductor layer and the second nitride semiconductor layer.

  In the method for manufacturing a semiconductor device of the present invention, the first nitride semiconductor layer may be undoped, n-type, or p-type.

  In the method for manufacturing a semiconductor device of the present invention, the step (c) of forming an active layer of the semiconductor laser device on the semiconductor substrate before the step (a), and the second after the step (b). And a step (d) of re-growing a p-type third nitride semiconductor layer on the nitride semiconductor layer, wherein the step (b) selectively etches the second nitride semiconductor layer. In the step (d), the portion of the second nitride semiconductor layer remaining at the bottom of the recess is made p-type, and the first nitride semiconductor layer and the second nitride semiconductor are formed. The layer and the third nitride semiconductor layer preferably form a current confinement structure that confines the current injected into the active layer. With such a configuration, a semiconductor laser device having an embedded current confinement structure can be manufactured with good reproducibility.

  In the method for manufacturing a semiconductor device of the present invention, step (b) is a step of selectively etching the second nitride semiconductor layer to form a recess, and the second nitridation is performed after step (b). Preferably, the method further includes a step (e) of forming ohmic electrodes in regions on both sides of the recess on the physical semiconductor layer and a step (f) of forming a gate electrode in the recess. With such a configuration, a heterojunction field effect transistor having a gate recess structure can be manufactured with good reproducibility.

  The method for manufacturing a semiconductor device of the present invention preferably further includes a step (g) of removing a portion remaining at the bottom of the recess in the second nitride semiconductor layer before the step (f).

  In the method for manufacturing a semiconductor device of the present invention, it is preferable that the photoelectrochemical etching is caused to react with an alkaline etchant while irradiating the second nitride semiconductor layer with light. In this case, the etchant is preferably potassium hydroxide, and the light is preferably ultraviolet light.

  A semiconductor laser device according to the present invention includes an active layer formed on a substrate and a current confinement structure formed on the active layer for confining a current injected into the active layer. A p-type first nitride semiconductor layer sequentially formed from the layer side, a second nitride semiconductor layer having a Fermi level larger than the first nitride semiconductor layer and having a recess, and a p-type The second nitride semiconductor layer is n-type except for the portion remaining at the bottom of the recess, and the portion remaining at the bottom of the recess is p-type. It is characterized by.

  According to the semiconductor laser device of the present invention, the current confinement structure has a p-type first nitride semiconductor layer sequentially formed from the active layer side, and a Fermi level as compared with the first nitride semiconductor layer. Since the second nitride semiconductor layer which is large and has a recess and the p-type third nitride semiconductor layer are included, the recess can be formed in the second nitride semiconductor layer with good reproducibility. . In addition, almost no etching damage occurs when the recess is formed. Therefore, it is possible to realize a semiconductor laser device having almost no variation in characteristics and deterioration.

  In the semiconductor laser device of the present invention, the portion remaining at the bottom of the recess in the second nitride semiconductor layer includes n-type impurities contained in other portions of the second nitride semiconductor layer, and the third A p-type impurity contained in the nitride semiconductor layer or the first nitride semiconductor layer may be included.

  According to the method for manufacturing a semiconductor laser device and a nitride semiconductor device according to the present invention, it is possible to realize a method for manufacturing a nitride semiconductor device in which device characteristic deterioration due to etching damage and device characteristic variation due to etching variation are small.

(First embodiment)
First, the principle of wet etching used in the method for manufacturing a semiconductor device according to the first embodiment of the present invention will be described with reference to the drawings. The wet etching used in this embodiment is a photoelectrochemical (PEC) etching in which a nitride semiconductor layer is reacted with an alkaline solution in a state where light is irradiated.

  FIG. 1 shows an outline of PEC etching. As shown in FIG. 1, a nitride semiconductor layer 51 connected to a cathode 52 made of platinum (Pt) or the like is immersed in an alkaline solution 53 such as potassium hydroxide (KOH), and is etched by irradiating light. Do. The PEC etching selectively etches the n-type nitride semiconductor, and the p-type nitride semiconductor is not etched.

  Etching an n-type nitride semiconductor by PEC etching has been described in various documents (for example, see Non-Patent Document 1). Therefore, when the n-type nitride semiconductor layer is stacked on the p-type nitride semiconductor layer, only the n-type nitride semiconductor layer is etched without etching the p-type nitride semiconductor layer. It is expected to etch. However, it is possible to selectively remove only the n-type nitride semiconductor layer by performing PEC etching after actually forming the n-type nitride semiconductor layer on the p-type nitride semiconductor layer. There has been no report.

  As a result of the study by the present inventors, when the PEC etching is performed on the n-type second nitride semiconductor layer formed on the p-type first nitride semiconductor layer, the etching is performed on the n-type first nitride semiconductor layer. Instead of proceeding to the interface between the two nitride semiconductor layers and the p-type first nitride semiconductor layer, the n-type second nitride semiconductor layer is stopped in a state where several nm to several tens of nm remain. It became clear.

  Thus, it is estimated that the PEC etching stops in the state where the n-type second nitride semiconductor layer remains several tens of nm for the following reason.

  FIG. 1A shows a first nitride semiconductor layer and a second nitride semiconductor when the first nitride semiconductor layer is a p-GaN layer and the second nitride semiconductor layer is n-AlGaN. The state of the energy band in the vicinity of the interface with the layer is shown. Compared to the n-type second nitride semiconductor layer, the p-type first nitride semiconductor layer has a lower Fermi level Ef. Therefore, the energy band rises as shown in FIG. 1A in the vicinity of the interface between the first nitride semiconductor layer and the second nitride semiconductor layer. PEC etching proceeds until the energy band rises, but at the point where the energy band rises, holes necessary for etching are not supplied to the interface between the etchant and the second nitride semiconductor layer, and etching stops. It is thought that. For this reason, it is estimated that the second nitride semiconductor layer remains by a thickness of several tens of nanometers from the interface between the second nitride semiconductor layer and the first nitride semiconductor layer.

  If the etching stops due to the rise of the energy band at the interface, a nitride having a smaller Fermi level than the second nitride semiconductor layer, even if the first nitride semiconductor layer is not p-type Any semiconductor layer may be considered.

  Actually, even when the first nitride semiconductor layer was n-type, PEC etching could be stopped with the second nitride semiconductor layer remaining several nm. FIG. 2B shows a band diagram in the case where the first nitride semiconductor is n-GaN, and the second nitride semiconductor layer is n-AlGaN having a Fermi level larger than that of the first nitride semiconductor. The band (Ev) of the valence band has the same bend as in FIG. For this reason, it is thought that PEC etching may stop.

  Further, the first nitride semiconductor may be an undoped layer. A band diagram in this case is shown in FIG. Also in this case, the band structure is the same as that shown in FIG. 2A, and the etching stops with the second nitride semiconductor remaining. Since the bending of the band generated in the n-AlGaN layer is smaller than that in the case of FIG. 2A, the remaining layer is thinner.

  The remaining amount of the second nitride semiconductor layer varies depending on the composition and doping amount of the first nitride semiconductor layer and the second nitride semiconductor layer. However, under the same conditions, the remaining amount can be controlled with excellent reproducibility. FIG. 3 shows the variation in film thickness of the remaining second nitride semiconductor layer when the first nitride semiconductor layer is n-type GaN and the second nitride semiconductor layer is n-type AlGaN. . In FIG. 3, the horizontal axis represents the test number, and the vertical axis represents the variation with respect to the average value of the film thickness. Etching was performed seven times, and the average film thickness was about 7 nm. As shown in FIG. 3, the variation in film thickness is ± 1.5 nm or less, and it is clear that the reproducibility is very good.

(Second Embodiment)
Hereinafter, as a second embodiment of the present invention, a method for manufacturing a semiconductor device using the PEC etching method shown in the first embodiment and a specific example of the semiconductor device manufactured thereby will be described with reference to the drawings. To do.

  FIG. 4 shows a cross-sectional configuration of the semiconductor device according to the second embodiment. As shown in FIG. 4, the semiconductor device of the second embodiment is a blue-violet semiconductor laser device having an embedded current confinement structure.

  On a substrate 11 made of GaN, an n-type GaN layer 12, an n-type cladding layer 13 made of n-type AlGaN, an n-type guide layer 14 made of n-type GaN, and a multiple quantum well made of InGaN ( An active layer 15 having an MQW structure and an overflow suppression layer 16 made of p-type AlGaN are sequentially formed from the substrate side.

  On the overflow suppression layer 16, a first p-type guide layer 17 made of p-type GaN, a current confinement layer 18 made of n-type AlGaN and having a recess, and a second p-type made of p-type GaN. A mold guide layer 19 is formed. A p-type cladding layer 20 made of p-type AlGaN and a p-type contact layer 21 made of p-type GaN are formed on the second p-type guide layer 19. A p-side electrode 22 is formed on the p-type contact layer 21, and an n-side electrode 23 is formed on the back surface of the substrate 11.

  An n-type current confinement layer 18 is sandwiched between the first p-type guide layer 17 and the second p-type guide layer 19. The p-side electrode 22 and the n-side electrode 23 are formed by a pn junction formed at the interface between the first p-type guide layer 17 and the current confinement layer 18 and at the interface between the second p-type guide layer 19 and the current confinement layer 18. The current between is interrupted. However, the portion 18a remaining at the bottom of the recess in the current confinement layer 18 has a thickness of about 15 nm and is p-type as will be described later. Therefore, the first p-type guide layer 17, the current confinement layer 18, and the second p-type guide layer 19 form a current confinement structure 24 that confines the current injected into the active layer 15. Thereby, a semiconductor laser device that emits light having a wavelength of 405 nm is obtained.

  A method for manufacturing the semiconductor laser device according to the second embodiment will be described below with reference to the drawings. FIG. 5 shows a method of manufacturing the semiconductor laser device of the second embodiment in the order of steps.

  First, as shown in FIG. 5A, on a substrate 11 made of GaN, a GaN layer 12, an n-type cladding layer 13, an n-type guide layer 14, an active layer 15, an overflow suppression layer 16, First p-type guide layer 17 and current confinement layer 18 are sequentially formed by metal organic chemical vapor deposition (MOCVD).

  Next, as shown in FIG. 5B, the current confinement layer 18 is selectively removed by the PEC etching method to form the recess 30. PEC etching may be performed, for example, using potassium hydroxide (KOH) as an etchant, platinum as a cathode, and irradiating ultraviolet rays. Further, it is preferable that the surface (back surface) of the substrate 11 on which the semiconductor layer is not formed does not touch the etchant during PEC etching. This is to prevent the nitrogen surface (Group V surface) of the substrate made of GaN from being selectively etched.

  As described above, the PEC etching automatically stops near the interface between the n-type nitride semiconductor layer and the p-type nitride semiconductor layer. In this case, the first p-type guide layer 17 corresponds to the first nitride semiconductor layer described in the first embodiment, and the n-type current confinement layer 18 corresponds to the second nitride semiconductor layer. For this reason, PEC etching automatically stops in a state where the current confinement layer 18 having a thickness of about 15 nm remains at the bottom of the recess 30.

  Next, as shown in FIG. 5C, the second p-type guide layer 19, the p-type cladding layer 20, and the p-type contact layer 21 are MOCVDed on the current confinement layer 18 in which the recess 30 is formed. Sequentially formed by the method. At this time, the p-type impurity contained in the second p-type guide layer 19 and / or the first p-type guide layer 17 diffuses into the current confinement layer 18. Normally, such diffusion can be ignored. However, in the recess 30, the thickness of the current confinement layer 18 is only about 15 nm. For this reason, the portion 18a remaining at the bottom of the recess 30 in the current confinement layer 18 becomes p-type. As a result, a current path through which a current flows is formed by the second p-type guide layer 19, the p-type portion 18 a of the current confinement layer 18, and the first p-type guide layer 17.

  Next, as shown in FIG. 5D, a multilayer film containing nickel (Ni) or palladium (Pd) is formed on the p-type contact layer 21 by electron beam (EB) vapor deposition, and then sintered. Thus, the p-side electrode 22 is formed. Further, after polishing the substrate 11 to a thickness of about 100 μm, a multilayer film containing titanium (Ti) is formed on the back surface of the substrate 11 by EB vapor deposition to form the n-side electrode 23. Finally, by performing chip separation, an embedded semiconductor laser device can be obtained.

  In the manufacturing method of the semiconductor laser device of this embodiment, the recess 30 formed in the current confinement layer 18 is formed by the PEC etching method. For this reason, compared with the case where it forms by dry etching, the damage which arises in a semiconductor layer is small, and the fall of the device characteristic by etching can be made small.

  Further, the second p-type guide layer 19 is regrown on the current confinement layer 18. In the conventional method of manufacturing a semiconductor laser device, an opening is formed in the current confinement layer to expose the first p-type guide layer. For this reason, the second p-type guide layer must be grown on the GaN in the opening and on the AlGaN in the other portions. Optimum crystal growth conditions differ between GaN and AlGaN, so it is difficult to obtain good crystallinity on both. For this reason, there is a problem that light absorption in the second p-type guide layer increases and the oscillation threshold current increases. However, in the manufacturing method of the semiconductor laser device of the present embodiment, since the underlying layer of the second p-type guide layer 19 is only the current confinement layer 18, uniform regrowth can be realized, and the oscillation threshold current can be increased. Can be suppressed.

  On the other hand, since the current confinement layer 18 made of AlGaN remains at the bottom of the recess 30, the resistance value of the current path may increase. However, the thickness of the current confinement layer 18 remaining at the bottom of the recess 30 is about 15 nm and can be almost ignored.

  FIG. 6 shows current-output characteristics of a semiconductor laser device actually manufactured by the manufacturing method of the second embodiment. A laser oscillation output of several tens of mW is obtained by an injection current of several tens of mA, which is comparable to a ridge stripe type semiconductor laser device.

  As described above, since the variation in the thickness of the current confinement layer 18 remaining at the bottom of the recess 30 is about ± 1.5 nm, it is possible to manufacture the semiconductor laser device with good reproducibility. . The thickness of the current confinement layer 18 remaining at the bottom of the recess 30 is changed in the range of several nm to several tens of nm depending on the composition of the first p-type guide layer 17 and the current confinement layer 18 and the impurity doping amount. Can do.

  In the present embodiment, GaN is used for the substrate, but any substrate may be used as long as the nitride semiconductor layer can be grown, and a substrate made of sapphire or silicon carbide may be used. Further, the first p-type guide layer and the current barrier layer need only have the Fermi level of the current barrier layer larger than the Fermi level of the first p-type guide layer, and have other compositions instead of GaN and AlGaN. Also good.

(Third embodiment)
The third embodiment of the present invention will be described below with reference to the drawings. FIG. 7 shows a cross-sectional configuration of the semiconductor device according to the third embodiment. As shown in FIG. 7, the semiconductor device of this embodiment is a heterojunction field effect transistor (HFET) having a gate recess structure.

  In the HFET of this embodiment, a buffer layer 42, a channel layer 43 made of undoped GaN, a surface barrier layer 44 made of undoped AlGaN, and a surface contact made of n-type GaN are formed on a substrate 41 made of sapphire. The layers 45 are sequentially formed from the substrate side.

  On the surface contact layer 45, ohmic electrodes 46 that are a source electrode and a drain electrode are formed at intervals. A gate recess portion 31 is formed in a region between the two ohmic electrodes 46 in the surface contact layer 45, and a gate electrode 47 is formed in the gate recess portion. In the HFET of this embodiment, the surface contact layer 45 having a thickness of several nanometers remains at the bottom of the gate recess, and the gate electrode 47 is in contact with the surface contact layer 45.

  Below, the manufacturing method of HFET concerning a 3rd embodiment is explained with reference to drawings. FIG. 8 shows the method of manufacturing the HFET of this embodiment in the order of steps. First, as shown in FIG. 8A, on a substrate 41 made of sapphire, a buffer layer 42, a channel layer 43 made of undoped GaN, a surface barrier layer 44 made of undoped AlGaN, and n-type GaN. The surface contact layer 45 made of is sequentially formed by MOCVD.

  Next, as shown in FIG. 8B, after forming a mask pattern 32 on the surface contact layer 45, PEC etching is performed to form a gate recess portion 31. PEC etching may be performed, for example, using potassium hydroxide (KOH) as an etchant, platinum as a cathode, and irradiating ultraviolet rays. A surface contact layer 45 having a thickness of several nanometers remains at the bottom of the formed gate recess 31.

  Next, as shown in FIG. 8C, after removing the mask pattern 32, a gate electrode 47 is formed in the gate recess portion 31, and the ohmic electrodes 46 are respectively formed on the surface contact layers 45 on both sides of the gate electrode 47. Form.

  Usually, when the surface contact layer 45 is etched to form the gate recess, dry etching is used. However, in the case of dry etching, the selectivity between the surface barrier layer 44 made of undoped AlGaN and the surface contact layer 45 made of n-type GaN is very small. Accordingly, in the case of dry etching, the etching amount varies for each wafer and within the wafer surface. As a result, the threshold voltage of the HFET varies. In the manufacturing method of this embodiment, etching can be stopped with good reproducibility in the vicinity of the interface between the surface contact layer 45 and the surface barrier layer 44. For this reason, it is possible to manufacture the HFET with a high yield. In general, when dry etching is used, the etching layer is damaged and the device characteristics are deteriorated. However, since the wet etching is used in the manufacturing method of this embodiment, the deterioration of the device characteristics can be suppressed.

  In the manufacturing method of the present embodiment, the surface contact layer 45 remains at the bottom of the gate recess 31. However, since the thickness of the remaining surface contact layer 45 is very thin, the occurrence of leakage current due to the remaining surface contact layer is in a negligible range. In particular, in this embodiment, the n-type GaN layer formed on the undoped AlGaN layer is removed by PEC etching. Thus, when the lower layer is undoped, the thickness of the remaining upper layer can be made thinner than when the lower layer is p-type, and the remaining amount is several nm. be able to.

  In the present embodiment, the surface barrier layer 44 is undoped AlGaN, but may be n-type AlGaN. In addition, the concentration of the two-dimensional electron gas can be increased by making the surface barrier layer 44 n-type.

  In order to increase the concentration of the two-dimensional electron gas, it is preferable that the concentration of the n-type impurity doped in the surface barrier layer 44 is higher. However, if the impurity concentration of the surface barrier layer 44 is too high, the Fermi level cannot be made smaller than that of the surface contact layer 45, and PEC etching may not stop. In this case, the impurity concentration may be reduced in the region in the vicinity of the interface with the surface contact layer 45 by using two surface barrier layers 44 or using a gradient material. Further, an undoped layer may be formed between the surface barrier layer 44 and the surface contact layer 45.

  As described above, the leakage current of the gate electrode hardly causes a problem, but the surface contact layer 45 remaining by PEC etching may be removed by dry etching. In this case, since the thin film layer having a thickness of several nanometers is dry-etched, the etching amount is very small, and there is almost no variation between wafers and within the wafer surface. In addition, since the etching amount is small, etching with low power is possible and damage to the etching layer hardly occurs.

  When the surface contact layer 45 is dry-etched, the entire surface contact layer 45 may be dry-etched, not just the portion remaining in the gate recess 31. This makes it possible to omit the step of forming a dry etching mask. Moreover, the effect that contact resistance can be reduced by forming an ohmic electrode after dry etching the surface of the surface contact layer 45 is also obtained.

  In this embodiment, sapphire is used as the substrate, but another substrate such as GaN or SiC may be used. Further, the surface barrier layer and the surface contact layer may have any other composition as long as the Fermi level of the surface contact layer is larger than the Fermi level of the surface barrier layer.

  In the first embodiment and the second embodiment, KOH is used as an etchant for PEC etching, but another alkaline solution may be used. In addition, other materials may be used for the cathode as long as the material has a higher ionization tendency than hydrogen. Further, the irradiation light may be light having energy larger than the band gap of the n-type nitride semiconductor layer to be etched.

  The method for manufacturing a nitride semiconductor device according to the present invention can realize a method for manufacturing a semiconductor device in which device characteristic deterioration due to etching damage and device characteristic variation due to etching variation are small, and semiconductor laser device and nitride semiconductor device manufacture This is useful as a method.

It is sectional drawing which shows the outline of the etching method which concerns on the 1st Embodiment of this invention. (A)-(c) is a band diagram which shows the relationship between the residual amount and the energy band of a nitride semiconductor layer in the etching method which concerns on the 1st Embodiment of this invention. It is a graph which shows the reproducibility of the etching method which concerns on the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the semiconductor laser apparatus which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the semiconductor laser apparatus concerning the 2nd Embodiment of this invention in order of a process. It is a graph which shows the relationship between the injection current and output of the semiconductor laser apparatus which concerns on the 2nd Embodiment of this invention. It is sectional drawing which shows the structure of the heterojunction field effect transistor which concerns on the 3rd Embodiment of this invention. It is sectional drawing which shows the manufacturing method of the heterojunction field effect transistor which concerns on the 3rd Embodiment of this invention in process order.

Explanation of symbols

11 Substrate 12 Buffer layer 13 n-type cladding layer 14 n-type guide layer 15 active layer 16 overflow suppression layer 17 first p-type guide layer 18 current confinement layer 18a portion 19 second p-type guide layer 20 p-type cladding layer 21 p-type contact layer 22 p-side electrode 23 n-side electrode 24 current confinement structure 30 recess 31 gate recess 32 mask pattern 41 substrate 42 buffer layer 43 channel layer 44 surface barrier layer 45 surface contact layer 46 ohmic electrode 47 gate electrode 51 nitride semiconductor Layer 52 Cathode 53 Solution

Claims (13)

A first nitride semiconductor layer and a second nitride semiconductor layer having a Fermi level larger than that of the first nitride semiconductor layer and containing an n-type impurity are sequentially formed on the substrate from the substrate side. Step (a) to perform,
The second nitride semiconductor layer is etched using photoelectrochemical etching, so that the etching is self-stopped with the second nitride semiconductor layer remaining, and the second nitride semiconductor layer is selected. And a step (b) for removing the nitride semiconductor device.   The etching stop position in the step (b) is controlled by a difference in Fermi level between the first nitride semiconductor layer and the second nitride semiconductor layer. Of manufacturing a nitride semiconductor device.   3. The nitriding according to claim 1, wherein the etching stop position in the step (b) is controlled by a carrier concentration of the first nitride semiconductor layer and the second nitride semiconductor layer. For manufacturing a semiconductor device.   The method of manufacturing a semiconductor device according to claim 1, wherein the first nitride semiconductor layer is undoped.   The method of manufacturing a semiconductor device according to claim 1, wherein the first nitride semiconductor layer is n-type.   The method for manufacturing a semiconductor device according to claim 1, wherein the first nitride semiconductor layer is p-type. (C) forming an active layer of a semiconductor laser device on the semiconductor substrate before the step (a);
A step (d) of re-growing a p-type third nitride semiconductor layer on the second nitride semiconductor layer after the step (b);
The step (b) is a step of selectively etching the second nitride semiconductor layer to form a recess.
In the step (d), a portion of the second nitride semiconductor layer remaining at the bottom of the recess is made p-type, and the first nitride semiconductor layer, the second nitride semiconductor layer, 2. The method of manufacturing a semiconductor device according to claim 1, wherein a current confinement structure for confining a current injected into the active layer is formed by the third nitride semiconductor layer. The step (b) is a step of selectively etching the second nitride semiconductor layer to form a recess.
After the step (b),
Forming an ohmic electrode in each of the regions on both sides of the recess on the second nitride semiconductor layer; and
The method of manufacturing a semiconductor device according to claim 1, further comprising a step (f) of forming a gate electrode in the recess.   9. The method according to claim 8, further comprising a step (g) of removing a portion remaining at the bottom of the recess in the second nitride semiconductor layer before the step (f). A method for manufacturing a semiconductor device.   10. The method of manufacturing a semiconductor device according to claim 1, wherein the photoelectrochemical etching is caused to react with an alkaline etchant while irradiating the second nitride semiconductor layer with light. . The etchant is potassium hydroxide,
The method of manufacturing a semiconductor device according to claim 10, wherein the light is ultraviolet light. An active layer formed on a substrate;
A current confinement structure formed on the active layer and confining a current injected into the active layer;
The current confinement structure includes a p-type first nitride semiconductor layer sequentially formed from the active layer side, a second Fermi level larger than that of the first nitride semiconductor layer, and a second portion having a recess. A nitride semiconductor layer and a p-type third nitride semiconductor layer;
The second nitride semiconductor layer is n-type except for a portion remaining at the bottom of the recess, and a portion remaining at the bottom of the recess is p-type.   The portion remaining in the bottom of the recess in the second nitride semiconductor layer is an n-type impurity contained in the other portion of the second nitride semiconductor layer, and the third nitride semiconductor layer. The semiconductor laser device according to claim 12, further comprising a p-type impurity contained in the first nitride semiconductor layer.

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