JP2009212139A - ZnO SEMICONDUCTOR ELEMENT - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ZnO semiconductor element which can suppress deterioration in the planarity of an acceptor-doped layer or in a layer formed after the acceptor-doped layer without deteriorating a concentration of an acceptor element, in the case of forming a laminated body which includes an acceptor-doped layer composed of a ZnO semiconductor. <P>SOLUTION: In the ZnO semiconductor element, an n-type Mg<SB>Z</SB>ZnO layer 2, an undoped MgZnO layer 3, an MQW active layer 4, an undoped Mg<SB>X</SB>ZnO layer 5 and an acceptor-doped Mg<SB>Y</SB>ZnO layer 6 are sequentially laminated on a ZnO substrate 1. The acceptor-doped Mg<SB>Y</SB>ZnO (0≤Y<1) layer 6 includes at least one acceptor element, and the undoped Mg<SB>X</SB>Zn<SB>1-X</SB>O (0<X<1) layer 5 is formed in contact with the layer. Therefore, the acceptor element can be sufficiently taken into the layer to be doped with the acceptor, and the surface planarity of the acceptor-doped layer is improved. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ZnO-based semiconductor element including an acceptor-doped layer made of ZnO or MgZnO in a laminated structure.

  ZnO-based semiconductors are expected to be applied to ultraviolet LEDs, high-speed electronic devices, surface acoustic wave devices and the like that are used as light sources for illumination, backlights, and the like. Although ZnO-based semiconductors have attracted attention for their multifunctionality, light emission potential, and the like, they have hardly grown as semiconductor device materials. The biggest difficulty is that acceptor doping is difficult and P-type ZnO cannot be obtained.

  However, as seen in Non-Patent Document 1 and Non-Patent Document 2, in recent years, P-type ZnO can be obtained due to technological advances, and light emission has been confirmed. Although it has been proposed to use nitrogen as an acceptor to obtain p-type ZnO, as shown in K. Nakahara et al., Journal of Crystal Growth 237-239 (2002) p.503, When doping nitrogen, the doping efficiency of nitrogen strongly depends on the growth temperature, and it is necessary to lower the substrate temperature in order to perform nitrogen doping. However, when the substrate temperature is lowered, the crystallinity is lowered and the acceptor is compensated. Since the carrier compensation center is formed and nitrogen is not activated (self-compensation effect), the formation of the p-type ZnO layer itself becomes very difficult.

 Therefore, as shown in Non-Patent Document 2, the main surface of growth is a -C plane, and the temperature dependence of the nitrogen doping efficiency is used to repeat the growth temperature between 400 ° C. and 1000 ° C. There is a method of forming a p-type ZnO layer having a high carrier concentration by a modulation method (Repeated Temperature Modulation: RTM).

 However, the above-described method has a problem that the expansion and contraction are repeated by continuous heating and cooling, so that the burden on the manufacturing apparatus is large, the manufacturing apparatus becomes large, and the maintenance cycle is shortened. Further, since the low temperature portion determines the doping amount, it is necessary to accurately control the temperature, but it is difficult to accurately control 400 ° C. and 1000 ° C. in a short time, and the reproducibility and stability are poor. Further, since a laser is used as a heating source, it is not suitable for heating a large area, and it is difficult to grow a large number of sheets for reducing the device manufacturing cost. RTM is necessary because, when the -C face of a ZnO substrate is used for crystal growth, nitrogen does not enter unless the temperature is lowered, which is unique to -C face growth.

On the other hand, it is already known that, for example, as shown in Non-Patent Document 3, it is easy to enter nitrogen when a + C plane of a ZnO substrate is used as a growth substrate. Therefore, as a result of conducting research to grow a ZnO-based thin film on a + C-plane ZnO substrate as a + C-plane, the MgZnO thin film is easier to be p-type than the ZnO thin film, and the constant temperature is maintained without using RTM. It has been found that p-type conversion is possible even in growth, which is described in detail in Japanese Patent Application No. 2007-251482, which has already been filed.
A. Tsukazaki et al., JJAP 44 (2005) L643 A. Tsukazaki et al Nture Material 4 (2005) 42 M. Sumiya et al., Applied Surface Science 223 (2004) p.206

  However, problems still remain even when the above-described method is used. This occurs when a stacked structure of semiconductor elements is produced. When laminating ZnO-based thin films, the flatness of the thin film is important. If the flatness of the thin film is not good, it becomes resistance when carriers move through the thin film, or the upper layer of the laminated structure, the surface roughness increases, and the etching depth cannot be uniform due to the surface roughness. Or the growth of anisotropic crystal planes due to surface roughness is likely to occur, and it is difficult to perform a desired function as a semiconductor device. Therefore, it is usually desired that the surface of the thin film be as flat as possible.

 In order to laminate a flat ZnO-based thin film, as shown in Japanese Patent Application Nos. 2008-5987 and 2007-27182, a growth temperature of 750 ° C. or higher is necessary. Thus, a flat film cannot be formed. On the other hand, when a ZnO-based thin film is grown on the + C plane, nitrogen easily enters, but the dependence on the growth temperature is not lost, and nitrogen becomes more difficult to enter as the temperature increases.

 In the case of a ZnO-based thin film n-type layer, there is no problem in doping with n-type impurities or film flatness even if the crystal is grown at a high temperature. However, when producing the acceptor doped layer, it is necessary to lower the growth temperature as described above in order to increase the acceptor element doping concentration. However, when the growth temperature is lowered, surface roughness of the film occurs. For this reason, when laminating a ZnO-based thin film, if an acceptor doped layer is laminated after the n-type layer is produced, surface roughness occurs in the acceptor doped layer. On the other hand, if an n-type layer is laminated after the acceptor-doped layer is produced, the n-type layer is formed. The roughness of the acceptor-doped layer propagates, resulting in poor surface flatness, and there is a problem that a desired function as a semiconductor device cannot be exhibited.

 The present invention was devised to solve the above-described problems, and acceptor doped layers can be formed without reducing the concentration of acceptor elements when forming a laminate including an acceptor doped layer made of a ZnO-based semiconductor. Alternatively, an object of the present invention is to provide a ZnO-based semiconductor element capable of suppressing deterioration in flatness of layers after the acceptor doped layer.

In order to achieve the above object, an invention according to claim 1 is a ZnO-based semiconductor element formed by laminating ZnO-based semiconductors on a substrate by crystal growth, wherein Mg _Y Zn _{1-Y 2} O (0 ≦ Y comprises an acceptor-doped layer comprising at least one acceptor element consists of <1) layer, the Mg in contact with the acceptor-doped layer is undoped or donor-doped _{X Zn 1-X O (0} <X <1) layer is formed It is a ZnO-based semiconductor element characterized by being made.

According to a second aspect of the present invention, there is provided a ZnO-based semiconductor element formed by laminating ZnO-based semiconductors on a substrate by crystal growth, wherein the Mg _Y Zn _1-Y O (0 ≦ Y <1) layer is used. the configured acceptor element and containing at least one acceptor-doped layer, the donor element and at least one n-type comprising the _{Mg Z Zn 1-Z O (} 0 ≦ Z <1) layer was the undoped or donor-doped Mg _X Zn _{1-X O} layer, wherein while located between the acceptor-doped layer and n-type Mg Z _Zn 1-Z _O layer, is formed in contact either 1-way between the two layers ZnO-based semiconductor element.

 The invention according to claim 3 is characterized in that the acceptor-doped layer is formed on the side closer to the substrate, and the ZnO-based semiconductor element according to any one of claims 1 and 2 It is.

The invention according to claim 4 is characterized in that the Mg composition X of the undoped or donor-doped Mg _X Zn _1-X O layer is in the range of 0 <X ≦ 0.5. 4. The ZnO-based semiconductor element according to claim 3.

 The invention according to claim 5 is the ZnO-based semiconductor device according to any one of claims 1 to 4, wherein at least one of the acceptor elements of the acceptor doped layer is nitrogen. It is.

The invention of claim 6, wherein at least one of the donor element of the n-type Mg Z _Zn 1-Z _O layer, any one of claims 1 to 5, characterized in that the III group element 2. A ZnO-based semiconductor element according to item 1.

According to the present invention, when a stacked body including an acceptor-doped layer made of a ZnO-based semiconductor is formed, an undoped or donor-doped MgZnO layer is formed in contact with the acceptor-doped layer. Also, if it contains an acceptor-doped layer and n-type _{Mg Z Zn 1-Z} O layer laminate, undoped or donor-doped MgZnO layer, between the acceptor-doped layer and n-type _{Mg Z Zn 1-Z} O layer And is in contact with either one of the two layers. Therefore, the deterioration of the flatness of the acceptor doped layer or the layers after the acceptor doped layer can be suppressed without lowering the acceptor element concentration of the acceptor doped layer due to the base effect of the MgZnO layer.

 Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a laminated structure of ZnO-based semiconductor elements of the present invention.

Growth n-type on the ZnO substrate 1 as the substrate _{Mg Z Zn 1-Z O (} 0 ≦ Z <1) layer 2, an undoped MgZnO layer 3, MQW active layer 4, the undoped _{Mg X Zn 1-X O (} 0 < An X <1) layer 5 and an acceptor-doped Mg _Y Zn _{1-Y 2} O (0 <Y <1) layer 6 are sequentially stacked. Here, n-type _{Mg Z Zn 1-Z} O layer 2, the undoped _{Mg X Zn 1-X} O layer 5, in order to simplify the notation, such as the acceptor-doped _{Mg Y Zn 1-Y} O layer 6, respectively, n type _Mg Z ZnO layer 2, an undoped _Mg X ZnO layer 5, referred to as the acceptor-doped _Mg Y ZnO layer 6. Hereinafter, the same applies to other notations.

 A ZnO-based semiconductor or a ZnO-based thin film is composed of ZnO or a compound containing ZnO. Specific examples include ZnO, IIA group element and Zn, IIB group element and Zn, or IIA. It means a material containing each group element, IIB group element and Zn oxide.

The MQW active layer 4 is formed in, for example, a multiple quantum well structure in which barrier layers Mg _0.15 ZnO and well layers ZnO are alternately stacked. The acceptor-doped Mg _Y ZnO layer 6 is doped with at least one acceptor element. As the acceptor element, nitrogen, phosphorus, arsenic, lithium, copper, or the like is used. The donor element added to the n-type Mg Z _ZnO layer 2, from among the group III elements, at least one is selected. Therefore, two or more types may be doped, and examples of donor elements include B (boron), Al (aluminum), and Ga (gallium).

The undoped Mg _X ZnO layer 5 corresponds to the undoped or donor-doped Mg _X Zn _1-X O (0 <X <1) layer described in the claims, and may be a donor-doped Mg _X ZnO layer. . The donor element in this case can be selected as in the case of the n-type Mg _Z ZnO layer 2. Further, as described above, the undoped Mg _X ZnO layer 5 is composed of MgZnO in which the Mg composition is in the range of 0 <X and Mg is always included. On the other hand, the upper limit of the Mg composition is preferably 0 <X ≦ 0.5. This is because the Mg composition ratio capable of producing a uniform MgZnO mixed crystal is currently 50% or less. To produce a uniform MgZnO mixed crystal more reliably, the Mg composition ratio may be 30% or less. Further preferred.

 Here, when ZnO (zinc oxide) or MgZnO (magnesium zinc oxide) is doped with a donor element, it usually becomes n-type. However, when an acceptor element is doped, self-compensation is possible depending on the doping amount. Since the acceptor element is not necessarily activated due to effects or the like and may not become a p-type semiconductor, the acceptor-doped layer includes a p-type semiconductor and an i-type semiconductor (intrinsic semiconductor).

 A characteristic point in the structure of FIG. 1 is that an undoped MgZnO layer is used as a base when an acceptor doped layer is formed. Thus, when laminating ZnO-based semiconductors, by inserting an undoped MgZnO layer between the n-type layer and the acceptor-doped layer, a large amount of acceptor elements can be taken into the acceptor-doped layer and the acceptor-doped layer. Surface roughness can be prevented.

 Hereafter, the said effect is demonstrated. First, as described in the background art, using the + C plane of the ZnO substrate and growing the ZnO-based thin film to the + C plane makes it easier for the acceptor element to enter, but the growth temperature dependency is not lost, and the higher the temperature, Acceptor elements are difficult to enter.

FIG. 5 shows the relationship between the crystal growth temperature (substrate temperature) and the nitrogen concentration in the ZnO thin film. This is a result of growing a ZnO thin film on the + C plane of the ZnO substrate while doping nitrogen, which is a kind of acceptor element. The vertical axis represents the nitrogen concentration (cm ⁻³ ) taken into the ZnO thin film when nitrogen is doped, and the horizontal axis represents the growth temperature (substrate temperature: unit ° C.). As shown in FIG. 3, in the ZnO-based thin film, the nitrogen concentration, which is a kind of acceptor element, has temperature dependence even when the + C plane is used, and the doped nitrogen concentration increases as the temperature decreases. Therefore, in order to sufficiently incorporate nitrogen and make the ZnO-based thin film p-type, the substrate temperature may be lowered. However, when the substrate temperature is lowered, the following surface flatness problem occurs. .

 The relationship between the surface flatness and the growth temperature in the case of forming a ZnO thin film is detailed in Japanese Patent Application No. 2008-5987 already filed, but the point will be described again. FIG. 7 shows the ZnO thin film grown on the MgZnO substrate by changing the substrate temperature (growth temperature), and the surface flatness of the ZnO for each substrate temperature is expressed as a numerical value. The vertical axis Ra (unit: nm) in FIG. 7 represents the arithmetic average roughness of the film surface. The arithmetic average roughness Ra is obtained from a roughness curve.

 The roughness curve is, for example, the unevenness of the film surface observed by AFM (atomic force microscope) measurement or the like measured at a predetermined sampling point, and the size of the unevenness together with the average value of these unevennesses. is there. Then, a reference length l is extracted from the roughness curve in the direction of the average line, and the absolute values of deviations from the average line of the extracted portion to the measurement curve are summed and averaged. Arithmetic mean roughness Ra = (1 / l) × ∫ | f (x) | dx (integral interval is 0 to l). By doing so, the influence of one scratch on the measured value becomes very small, and a stable result can be obtained. The surface roughness parameters such as the arithmetic average roughness Ra are defined by JIS standards and are used.

 FIG. 7 shows the arithmetic average roughness Ra calculated as described above on the vertical axis and the substrate temperature on the horizontal axis. The black triangle (▲) in FIG. 7 indicates data when the substrate temperature is less than 750 ° C., and the black circle (●) indicates data when the substrate temperature is 750 ° C. or higher. As can be seen from FIG. 7, it can be seen that the flatness of the surface is drastically improved when the substrate temperature becomes higher at the boundary of 750 ° C.

FIG. 8 shows the root mean square roughness RMS of the film surface obtained from the same measurement data as FIG. The root mean square roughness RMS is the sum of the squares of deviations from the mean line of the roughness curve to the measurement curve and represents the square root of the averaged value. Using the reference length l when calculating the arithmetic average roughness Ra,
RMS = {(1 / l) × ∫ (f (x)) ² dx} ^1/2 (the integration interval is from 0 to 1).

 FIG. 8 shows the root mean square roughness RMS on the vertical axis and the substrate temperature on the horizontal axis. Here, the black triangle (▲) indicates data when the substrate temperature is less than 750 ° C., and the black circle (●) indicates data when the substrate temperature is 750 ° C. or higher. As for the substrate temperature, it can be seen that the flatness of the surface is abruptly improved when the substrate temperature increases at 750 ° C. as in FIG.

 Therefore, when a ZnO-based thin film is grown on a ZnO-based material layer, a film with good flatness can be obtained by epitaxial growth at a substrate temperature of 750 ° C. or higher. can get.

 However, as shown in FIG. 5, even in the + C plane growth, the nitrogen doping amount depends on the growth temperature, and when the nitrogen doping amount is sufficiently obtained, the growth temperature of the ZnO-based thin film is set to less than 750 ° C. As shown in FIGS. 7 and 8, the surface flatness is extremely deteriorated when the temperature is lower than 750 ° C. In addition, the step flow growth temperature of MgZnO is higher than that of ZnO.

 FIG. 6 shows that the step flow growth temperature of MgZnO increases, and FIG. 6A shows an image obtained by scanning the surface of the ZnO thin film grown on the ZnO substrate in a range of 2 μm square using AFM, FIG. 6B is an image obtained by scanning the surface of the MgZnO thin film grown on the ZnO substrate in an area of 2 μm square using AFM.

 The ZnO thin film in FIG. 6A has a growth temperature of 790 ° C., and the growth temperature of the MgZnO thin film in FIG. In the MgZnO thin film, the surface flatness is maintained at a growth temperature of about 880 ° C., but in the ZnO thin film, the surface flatness is maintained even at 790 ° C. As described above, the MgZnO thin film needs to be grown at a higher temperature than the ZnO thin film. When the growth temperature is lowered to increase the nitrogen doping concentration, the influence on the surface flatness of the MgZnO thin film is larger. Conceivable.

As described in the already filed Japanese Patent Application No. 2007-221198, surface roughness of ZnO-based semiconductors causes unintentional impurity doping, which hinders p-type conversion. Among impurities, in particular, Si is a constituent element of a discharge tube in a radical cell that generates active oxygen by converting O ₂ into plasma, and is most often mixed. When Si is taken in, it works as a donor, so that the p-type conversion becomes difficult if the Si concentration increases. Therefore, it is important to flatten the film surface.

 Therefore, as shown in FIG. 1, when the acceptor-doped layer is produced, the surface flatness of the acceptor-doped layer is improved by using an undoped or donor-doped MgZnO layer as a base. FIG. 2 shows the difference in effect between when the MgZnO layer is used as a base and when it is not used when forming the acceptor doped layer. In FIG. 2A, a Ga-doped MgZnO layer 42, an undoped MgZnO layer 43, a stacked body 44, an undoped ZnO layer 45, and a nitrogen-doped MgZnO layer 46 are formed in this order on a ZnO substrate 41. The Ga-doped MgZnO layer 42 to the undoped ZnO layer 45 were grown at a growth temperature of 900 ° C., and the nitrogen-doped MgZnO layer 46 was grown at a low growth temperature of 830 ° C. in order to increase the nitrogen concentration.

 On the other hand, in FIG. 2B, a Ga-doped MgZnO layer 42, an undoped MgZnO layer 43, a stacked body 44, an undoped MgZnO layer 50, and a nitrogen-doped MgZnO layer 46 were formed in this order on the ZnO substrate 41. The Ga-doped MgZnO layer 42 to the undoped MgZnO layer 50 were grown at a growth temperature of 900 ° C., and the nitrogen-doped MgZnO layer 46 was grown at a low growth temperature of 830 ° C. in order to increase the nitrogen concentration.

The stacked body 44 is a superlattice layer, and is configured by a stacked body in which undoped ZnO and undoped MgZnO are alternately stacked for 10 periods. Moreover, Ga-doped MgZnO layer 42 is the n-type _Mg Z ZnO layer, nitrogen-doped MgZnO layer 46 in the acceptor-doped layer _(Mg Y ZnO layer), an undoped MgZnO layer 50 corresponds to the _Mg X ZnO layer which is undoped or donor-doped .

 In FIGS. 2A and 2B, other layer structures, growth temperatures, and the like are different depending on whether the undoped ZnO layer 45 or the undoped MgZnO layer 50 is used as the base of the nitrogen-doped MgZnO layer 46. Is the same. FIG. 3 shows a comparison of the surface states of these uppermost layers. 3A shows the surface of the uppermost nitrogen-doped MgZnO layer 46 shown in FIG. 2A, and FIG. 3B shows the surface of the uppermost nitrogen-doped MgZnO layer 46 shown in FIG. These are images scanned by AFM measurement. 3B has a clean surface with no roughness, and is considered to be an effect obtained by using the undoped MgZnO layer 50 as the base of the nitrogen-doped MgZnO layer 46 in FIG. 2B.

Next, a method for manufacturing the ZnO-based semiconductor element having the structure shown in FIG. 1 will be described. The + C plane ZnO substrate 1 is wet-etched with an acidic solution having a pH of 3 or less to remove the polishing damage layer. The ZnO substrate 1 is introduced into the MBE apparatus having a background vacuum of about 5 × 10 ⁻⁷ Pascal through the load lock chamber. While measuring the temperature by thermography, the ZnO substrate 1 is heated at 700 ° C. to 1000 ° C. to sublimate H ₂ O and hydrocarbon organic substances adhering to the atmosphere (thermal cleaning).

At a growth temperature of 900 ° C., a Ga-doped MgZnO layer / undoped MgZnO layer / MQW active layer is grown using a Ga-doped MgZnO layer as the n-type Mg _Z ZnO layer 2. The MQW active layer 4 is formed, for example, by repeating the well layer ZnO with a thickness of 1.5 nm and the barrier layer Mg _0.15 ZnO with a thickness of 6 nm for about 5 cycles. At this time, the MQW active layer 4 may include a ZnO layer. However, when the final layer of the MQW active layer 4 is a ZnO layer, for example, an undoped Mg on the MQW active layer 4 as shown in FIG. _{X An} undoped Mg _0.05 ZnO layer is formed at a growth temperature of 900 ° C. as the ZnO layer 5. Next, the growth temperature is lowered to 850 ° C., and NO (nitrogen monoxide) gas is introduced by plasma cracking to grow nitrogen-doped Mg _0.15 ZnO as the acceptor-doped Mg _Y ZnO layer 6.

 As described above, when an undoped MgZnO layer is used as the base of the acceptor doped layer, the surface flatness can be improved even when the growth temperature is lowered when the acceptor doped layer is formed, so that the acceptor element can be sufficiently incorporated. If this is applied, the present invention can be applied to elements other than the above-described light-emitting elements, such as MOS or MIS type FETs (field effect transistors), HEMTs (high electron mobility transistors), and the like.

 For example, when manufacturing a trench type MOSFET, there is an NPN structure having a p-type layer as a channel layer. When an NPN structure is manufactured, the substrate temperature is raised when the growth process shifts from the p-type layer to the n-type layer. At this time, if the p-type ZnO is the final layer of the p-type layer, Since ZnO tends to cause defects at a high temperature, p-type ZnO causes surface roughness, and further, surface roughness propagates to an n-type layer formed thereon to deteriorate surface flatness. Also in this case, by forming undoped MgZnO or donor-doped MgZnO on the upper layer of the p-type layer, the subsequent n-type layer can be formed without surface roughness.

An NPN structure is used for a MOS transistor, but only the layer structure is shown in FIG. An n-type MgZnO layer 22, an acceptor-doped ZnO layer 23, an undoped MgZnO layer 24, and an n-type MgZnO layer 25 are formed on the ZnO substrate 21. The acceptor doped MgZnO layer 23 becomes a p-type layer and forms an NPN structure. Since the acceptor-doped MgZnO layer 23 corresponding to the acceptor-doped layer is formed using the n-type MgZnO layer 22 corresponding to the donor-doped Mg _X Zn _1- XO layer as a base, the doping amount of the acceptor element can be ensured, The surface flatness of the acceptor doped MgZnO layer 23 is improved. Even if the surface flatness of the acceptor-doped MgZnO layer 23 deteriorates, the surface roughness does not propagate to the n-type MgZnO layer 25 because the n-type MgZnO layer 25 is formed with the undoped MgZnO layer 24 as a base. .

FIG. 4B shows an example of a laminated structure in which two acceptor-doped layers are formed. An acceptor-doped ZnO layer 32, an undoped MgZnO layer 33, an n-type ZnO layer 34, an acceptor-doped ZnO layer 35, an undoped MgZnO layer 36, and an n-type MgZnO layer 37 are formed on the ZnO substrate 31. Undoped MgZnO layers 33 and 36 (corresponding to undoped Mg _X Zn _1- XO layers) are formed on the upper layers of the acceptor doped MgZnO layers 32 and 35, respectively, and the surface roughness of the acceptor doped layer does not propagate to the upper layers. It is like that.

 In this way, by using an undoped MgZnO layer or a donor-doped MgZnO layer as a layer until the acceptor-doped layer is formed or after the acceptor-doped layer, deterioration of flatness of the acceptor-doped layer or higher layers is prevented. can do.

It is a figure which shows an example of the laminated structure of the ZnO type semiconductor element of this invention. It is a figure which shows the difference in the laminated structure at the time of using MgZnO and ZnO for the base | substrate of an acceptor dope layer. It is a figure which shows the state of the acceptor dope layer surface corresponding to each laminated structure of FIG. It is a figure which shows the other example of the laminated structure of the ZnO type semiconductor element of this invention. It is a figure which shows the growth temperature dependence of nitrogen concentration. It is a figure which shows the difference in the growth temperature in the case of producing flat MgZnO and ZnO. It is a figure which shows the relationship between the arithmetic mean roughness of a ZnO-type thin film surface, and a substrate temperature. It is a figure which shows the relationship between the root mean square roughness of a ZnO-type thin film surface, and a substrate temperature.

Explanation of symbols

1 ZnO substrate 2 n-type Mg _Z ZnO layer 3 undoped MgZnO layer 4 MQW active layer 5 undoped Mg _X ZnO layer 6 acceptor doped Mg _Y ZnO layer

Claims (6)

A ZnO-based semiconductor element formed by laminating ZnO-based semiconductors on a substrate by crystal growth,
_{Mg Y Zn 1-Y O (} 0 ≦ Y <1) comprising an acceptor-doped layer comprising at least one acceptor element consists of layers, the _Mg is undoped or donor-doped contact with the acceptor-doped layer X _{Zn 1-X} O A ZnO-based semiconductor element, wherein a (0 <X <1) layer is formed. A ZnO-based semiconductor element formed by laminating ZnO-based semiconductors on a substrate by crystal growth,
An acceptor doped layer composed of an Mg _Y Zn _1-Y O (0 ≦ Y <1) layer and containing at least one acceptor element, and an n-type Mg _Z Zn _1-Z O (0 ≦ 0) containing at least one donor element. And the undoped or donor-doped Mg _X Zn _1-X O layer is located between the acceptor doped layer and the n-type Mg _Z Zn _1-Z O layer, A ZnO-based semiconductor element, wherein the ZnO-based semiconductor element is formed in contact with any one of the layers.  The ZnO-based semiconductor element according to claim 1, wherein the acceptor-doped layer is formed closer to the substrate. 4. The Mg composition X of the undoped or donor-doped Mg _X Zn _1-X O layer is in a range of 0 <X ≦ 0.5. 5. ZnO-based semiconductor element.   5. The ZnO-based semiconductor device according to claim 1, wherein at least one of the acceptor elements in the acceptor-doped layer is nitrogen. 6. The ZnO-based semiconductor device according to claim 1, wherein at least one of donor elements in the n-type Mg _Z Zn _1-Z O layer is a group III element.