JP2005236157A - Semiconductor nano-wire element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a semiconductor nano-wire element having a high function. <P>SOLUTION: There is formed the semiconductor nano-wire element having on a gallium-phosphorus substrate 1 as its constituent elements a lower layer 2 made of gallium and phosphorus, an intermediate layer 3 made of indium and phosphorus, and an upper layer 4 made of gallium and phosphorus. The semiconductor nano-wire element is so constituted as to bury the whole of its nano-wires in a protective layer 5 in order to prevent the affection of the oxidation of each nano-wire, etc. which is caused by the atmospheric air. In each formed nano-wire, its diameter is 9-30 nm, and the lengths of its lower layer 2 and its upper layer 4 are 300 nm, and further, the thickness of its intermediate layer 3 is 10 nm. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a semiconductor nanowire element.

  In an optical device using a semiconductor material, when the device size is reduced, the quantum effect is affected. By utilizing this quantum effect, various characteristics of the optical device are expected to be improved. For example, application to a quantum dot laser or the like is also expected.

  When a semiconductor device is quantized, its energy level can be expressed as follows.

ここで（１）は一つの方向のみ量子化された二次元量子デバイス、（２）は二つの方向が量子化された一次元量子デバイス、（３）はすべての方向が量子化さ加たゼロ次元デバイスに対応し、それぞれ量子デイスク、量子ワイヤー、量子ボックス等と呼ばれる構造に対応する。また、ｌ、ｍ、ｎ（＝１、２、３、…）はそれぞれの方向に対応する量子準位、ｋ_ｙおよびｋ_ｚは、それぞれ、ｙおよびｚ方向の波数ベクトル、ｍ^＊は電子およびホールに対する有効質量、横棒つきのｈはプランク定数を２πで割った値、ｔ_ｘ、ｔ_ｙ、ｔ_ｚは、それぞれ、量子化が起こる領域のｘ、ｙ、ｚ方向の長さを示す。

Here, (1) is a two-dimensional quantum device that is quantized in only one direction, (2) is a one-dimensional quantum device that is quantized in two directions, and (3) is a zero that is quantized in all directions. It corresponds to a three-dimensional device and corresponds to a structure called a quantum disk, a quantum wire, a quantum box, or the like. Further, l, m, n (= 1, 2, 3,...) Are quantum levels corresponding to the respective directions, _ky and k _z are wave vector in the y and z directions, and m ^* is an electron and effective mass for holes, the value h of the horizontal bar with divided by Planck's constant by 2 [pi, t _{x, t y,} t _z, respectively, showing x regions quantization occurs, y, and z-direction length.

  By quantizing the energy levels in this way, the state density function is closer to the step function when the state density function is two-dimensional, and closer to the delta function when the state density function is one-dimensional and zero-dimensional. Benefits such as increased. This effect becomes more prominent as the quantization progresses. For example, the quantum wire that is a one-dimensional device or the quantum box that is a zero-dimensional device can be expected to improve characteristics than a quantum disk that is a two-dimensional device.

  Quantum devices currently in practical use are mainly two-dimensional devices in the formula (1), and examples include quantum well lasers (for example, see Non-Patent Document 1 below). In this case, there are features such as easy control of the oscillation wavelength of the quantum well laser and possible laser excitation with a low current. Many characteristics are improved by realizing a device using a two-dimensional or three-dimensional quantum effect. Is expected.

  However, in the case of a quantum well laser, the size is usually several hundred nm in diameter and several nm to several tens of nm in thickness, and it is only the thickness direction that satisfies the tenth nm, which is the size at which the quantum effect occurs. For this reason, in the case of a quantum well, quantization is a two-dimensional quantum device realized only in the vertical direction, and the use of the quantum effect is not yet sufficient.

  Semiconductor nanowires (quantum wires) with a cross-sectional size of several tens of nanometers and a length of several hundred nanometers are considered as one-dimensional quantum devices that are the next stage quantum devices. An attempt has been made to produce a quantum wire using a semiconductor substrate whose substrate surface is processed by lithography or the like (for example, see Non-Patent Document 1 below). However, this method uses selective growth due to the non-uniformity of the surface structure of the substrate, and when viewed at the micro level, it is difficult to perform precise shape control that affects the quantum effect.

  As another approach, nanowire fabrication using a metal catalyst-based VLS (Vapor-Liquid-Solid) mechanism has recently been attempted. As an example of a production method, an example using laser ablation and chemically reactive molecular beam epitaxy has been published, and precise size control can be performed by changing the size of the metal catalyst particles (for example, the following non-specification). (See Patent Documents 2 and 3).

  Moreover, the diameter of the obtained nanowire can be realized up to several nanometers, and is a size that can sufficiently exhibit the quantum effect. However, at present, the application of these nanowires is limited to electronic devices, and there is almost no application to optical devices. Also, in examples where nanowires are applied to optical devices, the nanowires separated from the substrate are appropriately dispersed, and only those that happen to be placed on the electrodes are used as optical devices. I don't have it. Furthermore, when a practical device manufacturing process is considered, there is a problem that good process control is not easy with such a method.

Book: “Physics and Applications of Semiconductor Superlattices”, Baifukan. Academic papers: X. Duan et al., Applied Physics Letters, vol. 67, p. 1116, 2000. Academic papers: J. et al. Ohlsson, Applied Physics Letters, vol. 79, p. 3335.2001). Academic papers: I. Mic et al. Phys. Chem., B, vol. 101, p. 4094, 1997.

  An object of the present invention is to solve the problem that the application of the conventional semiconductor nanowire element is limited because only the wire size effect has been used, and to provide a highly functional semiconductor nanowire element.

In the present invention, in order to achieve the above object, as described in claim 1,
A semiconductor nanowire device having a three-layer structure comprising three semiconductor layers having at least two different compositions, wherein an intermediate layer sandwiched between an upper layer and a lower layer of the three-layer structure is a band of the upper layer The semiconductor nanowire device is formed of a direct transition material having a smaller band gap than both the gap and the band gap of the lower layer, and has a width of 30 nm or less and a thickness of 30 nm or less.

In the present invention, as described in claim 2,
2. The semiconductor nanowire element according to claim 1, wherein the intermediate layer has a laminated structure including three or more subdivided layers, and the laminated structure is formed by any one of the band gap of the upper layer and the band gap of the lower layer. A first subdivided layer made of a semiconductor material having a bandgap that is not too large, and a second subdivided layer made of a direct transition type semiconductor material having a bandgap smaller than the bandgap of the first subdivided layer A semiconductor nanowire element characterized by being alternately stacked is formed.

In the present invention, as described in claim 3,
2. The semiconductor nanowire element according to claim 1, wherein the upper layer and the lower layer are made of gallium phosphide, and the intermediate layer is made of indium phosphide.

In the present invention, as described in claim 4,
2. The semiconductor nanowire element according to claim 1, wherein the upper layer and the lower layer are made of gallium arsenide, and the intermediate layer is made of indium arsenide.

  By implementing the present invention, it is possible to provide a highly functional semiconductor nanowire element.

  In the present invention, as means for achieving the above object, a three-layer semiconductor three-layer structure is formed on a substrate, semiconductor nanowires are formed therein, an upper layer of the semiconductor three-layer structure, and By making the band gap of the lower layer larger than that of the intermediate layer, it is possible to prevent carriers from penetrating into the upper layer and the lower layer, and to make the intermediate layer an ideal zero-dimensional quantum device.

  In this case, the band gap of the material constituting the upper layer and the lower layer may be larger than that of the intermediate layer, and basically any combination is possible as long as the material is such a combination. For example, gallium phosphide may be selected for the upper and lower layers, indium phosphide may be selected for the intermediate layer, gallium arsenide may be selected for the upper and lower layers, and indium arsenide may be selected for the intermediate layer. In addition, gallium arsenide may be selected for the upper layer and the lower layer, gallium antimony may be selected for the intermediate layer, selenium sulfide may be selected for the upper layer and the lower layer, and gallium arsenide may be selected for the intermediate layer. .

  Furthermore, for example, any two types of materials having close lattice constants listed in Table 1 are selected, materials having a large band gap are used for the upper layer and the lower layer, and materials having a small band gap are selected for the intermediate layer. May be.

  The intermediate layer is made of a direct transition material in which a direct transition between electron levels subjected to a quantum effect occurs.

  Furthermore, the intermediate layer is laminated, and the active layer with a small band gap is sandwiched by a barrier layer whose band gap is larger than the band gap of the active layer and not larger than the band gap of the upper layer and the band gap of the lower layer and the active layer The characteristics may be improved by making the thickness of the layer less than the thickness at which the quantum size effect occurs.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  A conceptual diagram of an embodiment of the present invention is shown in FIG.

  In this example, a nanowire composed of a gallium phosphide lower layer 2, an indium phosphide intermediate layer 4 and a gallium phosphide upper layer 3 was formed on the gallium phosphide substrate 1. The entire nanowire is embedded in the protective layer 5 in order to prevent the influence of oxidation or the like by the atmosphere. The diameter of the nanowire produced here is approximated by the width of the indium phosphide intermediate layer 4 (horizontal width in FIG. 1), which is 9 to 30 nm, and the lengths of the lower layer 2 and the upper layer 3 are 300 nm. The thickness of the intermediate layer 4 is 10 nm.

Next, the optical characteristics of the nanowire produced this time were evaluated by photoluminescence measurement. The measurement temperature was 10K, and a dye laser was used as the light source. The excitation energy of the laser was fixed at 2.2 eV, which is smaller than the excitation energy of gallium phosphorus and capable of emitting indium phosphorus. The energy of the laser is 1 × 10 ⁻⁷ J / cm ² .

  FIG. 2 shows the measured photoluminescence spectrum. (A) corresponds to the emission spectrum of the bulk crystal, and (b) to (g) correspond to the emission spectrum when the diameter of the nanowire is changed from 9.0 nm to 30 nm, respectively. When the nanowire diameter is 30 nm, the shift amount from the bulk peak (so-called blue shift value) is not so large as about 0.05 eV, but the shift amount increases as the wire diameter decreases. I understand. Note that the half-value width of the emission peak increases as the wire diameter decreases, but this reflects the fact that the greater the quantum effect, the more sensitive the wire diameter is, and the light emission from each wire. The half width of the peak is expected to be sufficiently small.

  FIG. 3 shows the relationship between the peak intensity energy shift amount and the wire diameter. When the wire diameter is reduced, the energy shift amount of the peak intensity is increased. In particular, when the wire diameter is 15 nm or less, the shift amount increases rapidly. This indicates that the influence of the quantum effect is increased below 15 nm. The calculated values shown in the figure are values obtained from the emission spectrum of InP colloidal particles (described in Non-Patent Document 4 above), which are almost the same as the actually measured values. Thus, it can be seen that an element having a sufficient quantum confinement effect was obtained. Furthermore, in this measurement, the laser energy required for light emission decreases as the diameter decreases, indicating that the present invention is superior.

  As described above, a semiconductor nanowire element having a three-layer structure including three semiconductor layers having at least two different compositions, and an intermediate layer sandwiched between an upper layer and a lower layer of the three-layer structure, A semiconductor nanowire device comprising a direct transition material having a band gap smaller than both of an upper layer band gap and a lower layer band gap, and having a width of 30 nm or less and a thickness of 30 nm or less. Can be produced. If the length of the intermediate layer 4 is 100 nm or more, characteristics as nanowires appear, and if the length is made shorter than that, the characteristics approach those of a quantum box.

  When such a semiconductor nanowire element is used as a component of an optical device, the excitation energy of external light or external electric field during device operation is greater than the intermediate layer band gap of the intermediate active layer, and the upper and lower barrier layers. Below the band gap of some upper and lower layers.

  Moreover, the intermediate layer 4 can be made into a multilayer structure, and the performance as an optical device can be further enhanced. That is, the intermediate layer 4 has a laminated structure composed of three or more subdivided layers, and the laminated structure is made of a semiconductor material having a band gap that is not larger than either the band gap of the upper layer 3 or the band gap of the lower layer 2. The first subdivided layer and the second subdivided layer made of a direct transition type semiconductor material having a band gap smaller than the band gap of the first subdivided layer are alternately stacked. Then, a semiconductor nanowire element as a higher performance optical device can be obtained.

  In addition, said semiconductor nanowire element can be produced in the arbitrary positions on a board | substrate, and the integration is also easy.

  As described above, by using the present invention, it has become possible to add functions to semiconductor nanowires, which has been difficult in the past, and to realize high-performance optical devices using the quantum effect. It is possible to contribute to the manufacturing technology of high-performance optical devices that can contribute to the development of

It is a figure explaining the concept of the Example of this invention. It is a figure which shows the emission spectrum from the semiconductor nanowire element by this invention. It is a figure which shows the relationship between the peak intensity energy shift amount and the wire diameter in the semiconductor nanowire element by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Board | substrate, 2 ... Lower layer, 3 ... Upper layer, 4 ... Intermediate | middle layer, 5 ... Protective layer.

Claims (4)

  A semiconductor nanowire device having a three-layer structure comprising three semiconductor layers having at least two different compositions, wherein an intermediate layer sandwiched between an upper layer and a lower layer of the three-layer structure is a band of the upper layer A semiconductor nanowire device comprising a direct transition material having a band gap smaller than any of the gap and the band gap of the lower layer, and having a width of 30 nm or less and a thickness of 30 nm or less.   2. The semiconductor nanowire element according to claim 1, wherein the intermediate layer has a laminated structure including three or more subdivided layers, and the laminated structure is formed by any one of the band gap of the upper layer and the band gap of the lower layer. A first subdivided layer made of a semiconductor material having a bandgap that is not too large, and a second subdivided layer made of a direct transition type semiconductor material having a bandgap smaller than the bandgap of the first subdivided layer A semiconductor nanowire element characterized by being alternately stacked.   2. The semiconductor nanowire element according to claim 1, wherein the upper layer and the lower layer are made of gallium phosphorus, and the intermediate layer is made of indium phosphorus.   2. The semiconductor nanowire element according to claim 1, wherein the upper layer and the lower layer are made of gallium arsenide, and the intermediate layer is made of indium arsenide.

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