JP2016062937A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device which has improved performance and improved reliability.SOLUTION: A semiconductor device comprises: a substrate 10; and a GaN-based semiconductor layer 11 which is formed on the substrate 10 by epitaxy and has a boron (B) concentration of equal to or lower than 1×10cm. The GaN-based semiconductor layer 11 includes an active layer 16 which is provided between the n-type GaN-based semiconductor layer 14 and the p-type GaN-based semiconductor layer 18 and has a multiquantum well structure.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a semiconductor device.

  GaN-based semiconductors such as GaN and AlGaN are used as materials for semiconductor light emitting devices and next-generation power semiconductor devices. In an element using a GaN-based semiconductor, there is a characteristic deterioration factor unique to the material. In order to realize a GaN-based semiconductor device having high performance and high reliability, it is necessary to take measures against the characteristic deterioration factors specific to the material.

JP 2001-85739 A

  An object of the present invention is to provide a semiconductor device with improved performance and reliability.

The semiconductor device according to the embodiment includes a substrate and a GaN-based semiconductor layer formed on the substrate by an epitaxial growth method and having a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less.

1 is a schematic cross-sectional view of a semiconductor device according to a first embodiment. The figure which shows the relationship between the boron concentration of the semiconductor device of 1st Embodiment, and the fluctuation rate of an operating current. FIG. 6 is a schematic cross-sectional view of a semiconductor device according to a second embodiment. FIG. 6 is a schematic cross-sectional view of a semiconductor device according to a third embodiment. FIG. 6 is a schematic cross-sectional view of a semiconductor device according to a third embodiment.

  In the present specification, the same or similar members are denoted by the same reference numerals, and redundant description may be omitted.

  In this specification, “GaN-based semiconductor” is a generic term for semiconductors having GaN (gallium nitride), AlN (aluminum nitride), InN (indium nitride), and intermediate compositions thereof.

  In the present specification, “upper” and “lower” are terms indicating the relative positional relationship of the constituent elements, and do not necessarily indicate the vertical relationship with respect to the direction of gravity.

(First embodiment)
The semiconductor device according to the present embodiment includes a substrate and a GaN-based semiconductor layer formed on the substrate by an epitaxial growth method and having a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less.

  FIG. 1 is a schematic cross-sectional view of the semiconductor device of this embodiment. The semiconductor device of this embodiment is a ridge waveguide type semiconductor laser using a GaN-based semiconductor.

  As shown in FIG. 1, the semiconductor device of this embodiment includes an n-type GaN substrate 10 and a GaN-based semiconductor layer 11. The GaN-based semiconductor layer 11 includes an n-type AlGaN cladding layer 12, an n-type GaN light guide layer 14, an active layer 16, a p-type AlGaN overflow prevention layer 18, a p-type GaN light guide layer 20, a p-type AlGaN cladding layer 22, p A type GaN contact layer 24 is provided.

  A ridge waveguide 26 is formed by a part of the p-type AlGaN cladding layer 22 and the p-type GaN contact layer 24. The side surface of the ridge waveguide 26 and the upper surface of the p-type AlGaN cladding layer 22 are covered with a protective film 28 of an insulating film. The protective film 28 is, for example, a silicon oxide film.

  A p-type electrode 30 is provided on the p-type GaN contact layer 24. The p-type electrode 30 is a metal electrode. An n-type electrode 32 is provided on the lower surface of the n-type GaN substrate 10. The n-type electrode 32 is a metal electrode.

  The active layer 16 has a GaN-based semiconductor multiple quantum well (MQW) structure. The active layer 30 is formed by a stacked structure of a well layer and a barrier layer. For the well layer and the barrier layer, for example, an InGaN layer having a different In concentration is used.

At least one of the layers constituting the GaN-based semiconductor layer 11 has a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less. It is desirable that at least one of the layers constituting the GaN-based semiconductor layer 11 has a boron (B) concentration of 1 × 10 ¹⁶ cm ⁻³ or less.

In particular, the boron (B) concentration of the active layer 16 is desirably 1 × 10 ¹⁷ cm ⁻³ or less, and more desirably 1 × 10 ¹⁶ cm ⁻³ or less.

  Next, a method for manufacturing the semiconductor device of this embodiment will be described. In this embodiment, the GaN-based semiconductor layer 11 is grown on the n-type GaN substrate 10 by metal organic chemical vapor deposition (MOCVD). The GaN-based semiconductor layer 11 is a single crystal layer formed by an epitaxial growth method.

  In the present embodiment, a member that does not contain boron (B) is selected and used as the member in the growth furnace for forming the GaN-based semiconductor layer 11 and the member in contact with the gas necessary for crystal growth. The member in the growth furnace is, for example, a susceptor on which a substrate is placed. The gas necessary for crystal growth is, for example, an organic metal gas, a group V gas, a carrier gas, or the like.

  Examples of the member not containing boron (B) include a silicon carbide (SiC) member and a quartz member. Examples of the member containing boron (B) include a boron nitride (BN) member.

  First, the n-type GaN substrate 10 is placed on a susceptor in a growth furnace. Then, a deposition gas is supplied into the growth furnace, and an n-type AlGaN cladding layer 12, an n-type GaN light guide layer 14, an active layer 16, a p-type AlGaN overflow prevention layer 18, on the n-type GaN substrate 10, A p-type GaN optical guide layer 20, a p-type AlGaN cladding layer 22, and a p-type GaN contact layer 24 are epitaxially grown in this order.

  Next, the p-type GaN contact layer 24 and a part of the p-type AlGaN cladding layer 22 are etched to form a ridge waveguide 26. Next, for example, a protective film 28 of a silicon oxide film is formed on the entire surface other than the upper portion of the ridge waveguide 26.

  Next, a p-type electrode 30 is formed on the p-type GaN contact layer 24, and an n-type electrode 32 is formed on the lower surface of the n-type GaN substrate 10.

  For example, silicon (Si) is used as the n-type impurity of the GaN-based semiconductor. In addition, as the p-type impurity of the GaN-based semiconductor, for example, magnesium (Mg) is used.

  Next, after the p-type electrode 30 and the n-type electrode 32 are formed, the chip is divided into individual chips by scribe or the like. With the above manufacturing method, the ridge waveguide type semiconductor laser shown in FIG. 1 is manufactured.

  Next, functions and effects of the semiconductor device of this embodiment will be described.

The GaN-based semiconductor layer 11 of the semiconductor device of this embodiment has a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less. As a result of studies by the inventors, it has been clarified that fluctuations in operating current are suppressed by reducing the boron (B) concentration of the GaN-based semiconductor layer 11, particularly the active layer 16.

  FIG. 2 is a diagram showing the relationship between the boron concentration and the operating current fluctuation rate of the semiconductor device of this embodiment. The semiconductor laser of this embodiment was incorporated into a package, and the operating current of the laser with an output of 10 mW was measured initially and after 40 hours of energization to determine the operating current fluctuation rate. Measurements were performed on samples having different boron concentrations in the active layer, and the relationship between the boron concentration and the fluctuation rate of the operating current was determined.

  The boron concentration was determined by SIMS (Secondary Ion Mass Spectrometry). Samples with different boron concentrations were prepared by changing the number of boron-containing members in the reactor.

  As is apparent from FIG. 2, the fluctuation rate of the operating current increases as the boron concentration in the active layer increases. Presumably, the presence of boron in the crystal of the GaN-based semiconductor forms a deep non-luminous level or crystal defect, resulting in a decrease in luminous efficiency. For this reason, it is considered that the operating current for obtaining the same laser output increases.

The GaN-based semiconductor layer 11 of the semiconductor device of this embodiment has a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less. Accordingly, deep non-luminous levels and crystal defects are reduced, and fluctuations in operating current are suppressed.

As is apparent from FIG. 2, the fluctuation rate of the operating current is suppressed to 10% or less by setting the boron concentration to 1 × 10 ¹⁷ cm ⁻³ or less. By setting the boron concentration of the GaN-based semiconductor layer 11 to 1 × 10 ¹⁶ cm ⁻³ or less, fluctuations in operating current can be further suppressed.

  According to this embodiment, a semiconductor laser in which fluctuations in operating current are suppressed can be realized.

  As described above, according to the semiconductor device of this embodiment, performance and reliability are improved.

(Second Embodiment)
The semiconductor device of this embodiment is different from that of the first embodiment in that it is a flip chip type LED (Light Emitting Device). Hereinafter, the description overlapping with the first embodiment will be omitted.

  FIG. 3 is a schematic cross-sectional view of the semiconductor device of this embodiment. The semiconductor device of this embodiment is a flip chip type LED.

  As shown in FIG. 3, the semiconductor device of this embodiment includes a sapphire substrate (substrate) 40 and a GaN-based semiconductor layer 41. The GaN-based semiconductor layer 41 includes a GaN buffer layer 42, an n-type GaN layer 44, an active layer 46, a p-type AlGaN layer 48, and a p-type GaN layer 50.

  A p-type electrode 52 is provided on the p-type GaN layer 50. The p-type electrode 52 is a metal electrode. An n-type electrode 54 is provided on the n-type GaN layer 44. The n-type electrode 54 is a metal electrode.

  The active layer 46 includes a GaN-based semiconductor multiple quantum well (MQW) structure. The active layer 46 is formed by a stacked structure of a well layer and a barrier layer. For the well layer and the barrier layer, for example, an InGaN layer having a different In concentration is used.

At least one of the layers constituting the GaN-based semiconductor layer 41 has a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less. It is desirable that at least one of the layers constituting the GaN-based semiconductor layer 41 has a boron (B) concentration of 1 × 10 ¹⁶ cm ⁻³ or less.

In particular, the boron (B) concentration of the active layer 46 is desirably 1 × 10 ¹⁷ cm ⁻³ or less, and more desirably 1 × 10 ¹⁶ cm ⁻³ or less.

  Next, a method for manufacturing the semiconductor device of this embodiment will be described. In this embodiment, the GaN-based semiconductor layer 41 is grown on the sapphire substrate 40 by metal organic chemical vapor deposition (MOCVD). The GaN-based semiconductor layer 41 is a single crystal layer formed by an epitaxial growth method.

  In the present embodiment, as in the first embodiment, a member that does not contain boron (B) is selected as the member in the growth furnace for forming the GaN-based semiconductor layer 41 and the member in contact with the gas necessary for crystal growth. use.

  First, the sapphire substrate 40 is placed on a susceptor in the growth furnace. Then, a deposition gas is supplied into the growth furnace, and the GaN buffer layer 42, the n-type GaN layer 44, the active layer 46, the p-type AlGaN layer 48, and the p-type GaN layer 50 are sequentially epitaxially grown on the sapphire substrate 40. Let

  Next, the p-type GaN layer 50 to the middle of the n-type GaN layer 44 are etched. Next, a p-type electrode 52 is formed on the p-type GaN layer 50, and an n-type electrode 54 is formed on the n-type GaN layer 44.

  Thereafter, the chip is divided into individual chips by scribing or the like. The flip chip type LED shown in FIG. 3 is manufactured by the above manufacturing method.

  In the flip chip type LED of the present embodiment, the boron concentration of the GaN-based semiconductor layer 41 is reduced, thereby reducing non-luminous deep levels and crystal defects. Therefore, an LED having excellent luminous efficiency and suppressed fluctuations in operating current is realized.

  As described above, according to the semiconductor device of this embodiment, performance and reliability are improved.

(Third embodiment)
The semiconductor device of this embodiment is different from the first embodiment in that it is an LED using a GaN substrate. Hereinafter, the description overlapping with the first embodiment will be omitted.

  FIG. 4 is a schematic cross-sectional view of the semiconductor device of this embodiment. The semiconductor device of this embodiment is an LED that uses a GaN substrate.

  As shown in FIG. 4, the semiconductor device of this embodiment includes a GaN substrate (substrate) 60 and a GaN-based semiconductor layer 61. The GaN-based semiconductor layer 61 includes a GaN buffer layer 62, an n-type GaN layer 64, an active layer 66, a p-type AlGaN layer 68, and a p-type GaN layer 70.

  A p-type electrode 72 is provided on the p-type GaN layer 70. The p-type electrode 72 is a metal electrode. An n-type electrode 74 is provided on the lower surface of the GaN substrate 60. The n-type electrode 74 is a metal electrode.

  The active layer 66 has a GaN-based semiconductor multiple quantum well (MQW) structure. The active layer 66 is formed by a stacked structure of a well layer and a barrier layer. For the well layer and the barrier layer, for example, an InGaN layer having a different In concentration is used.

At least one of the layers constituting the GaN-based semiconductor layer 61 has a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less. It is desirable that at least one of the layers constituting the GaN-based semiconductor layer 61 has a boron (B) concentration of 1 × 10 ¹⁶ cm ⁻³ or less.

In particular, the boron (B) concentration of the active layer 66 is desirably 1 × 10 ¹⁷ cm ⁻³ or less, and more desirably 1 × 10 ¹⁶ cm ⁻³ or less.

  The GaN-based semiconductor layer 61 of the present embodiment is formed on the GaN substrate 60 by the same method as in the first and second embodiments.

  In the LED of this embodiment, the boron concentration of the GaN-based semiconductor layer 61 is reduced, so that deep non-luminous levels and crystal defects are reduced. Therefore, an LED having excellent luminous efficiency and suppressed fluctuations in operating current is realized.

  As described above, according to the semiconductor device of this embodiment, performance and reliability are improved.

(Fourth embodiment)
The semiconductor device of this embodiment is different from that of the first embodiment in that it is a HEMT (High Electron Mobility Transistor). Hereinafter, the description overlapping with the first embodiment will be omitted.

  FIG. 5 is a schematic cross-sectional view of the semiconductor device of this embodiment. The semiconductor device of the present embodiment is a HEMT using a GaN-based semiconductor.

  As shown in FIG. 5, the semiconductor device of this embodiment includes a GaN substrate (substrate) 80 and a GaN-based semiconductor layer 81. The GaN-based semiconductor layer 81 includes a buffer layer 82, a GaN channel layer 84, and an AlGaN barrier layer 86.

  A gate electrode 88, a source electrode 90, and a drain electrode 92 are provided on the AlGaN barrier layer 86. A Schottky contact is provided between the AlGaN barrier layer 86 and the gate electrode 88. The AlGaN barrier layer 86 is in ohmic contact with the source electrode 90 and the drain electrode 92.

At least one of the layers constituting the GaN-based semiconductor layer 81 has a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less. It is desirable that at least one of the layers constituting the GaN-based semiconductor layer 81 has a boron (B) concentration of 1 × 10 ¹⁶ cm ⁻³ or less.

  The GaN-based semiconductor layer 81 of this embodiment is formed on the GaN substrate 80 by the same method as in the first and second embodiments.

  In the HEMT of the present embodiment, deep levels and crystal defects are reduced by reducing the boron concentration of the GaN-based semiconductor layer 81. Therefore, a HEMT with high breakdown voltage and low current leakage is realized.

  As described above, according to the semiconductor device of this embodiment, performance and reliability are improved.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. For example, a component in one embodiment may be replaced or changed with a component in another embodiment. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

10 n-type GaN substrate (substrate)
11 GaN-based semiconductor layer 14 n-type GAN optical guide layer (n-type GaN-based semiconductor layer)
16 Active layer 20 p-type GaN light guide layer (p-type GaN-based semiconductor layer)
40 Sapphire substrate (substrate)
41 GaN-based semiconductor layer 44 n-type GaN layer (n-type GaN-based semiconductor layer)
46 Active layer 48 p-type AlGaN layer (p-type GaN-based semiconductor layer)
60 GaN substrate (substrate)
61 GaN-based semiconductor layer 64 n-type GaN layer (n-type GaN-based semiconductor layer)
66 Active layer 68 p-type AlGaN layer (p-type GaN-based semiconductor layer)
80 GaN substrate (substrate)
81 GaN-based semiconductor layer

Claims (2)

A substrate,
A GaN-based semiconductor layer formed on the substrate by an epitaxial growth method and having a boron (B) concentration of 1 × 10 ¹⁷ cm ⁻³ or less;
A semiconductor device comprising: The GaN-based semiconductor layer is provided between an n-type GaN-based semiconductor layer, a p-type GaN-based semiconductor layer, and the n-type GaN-based semiconductor layer and the p-type GaN-based semiconductor layer, and has a multiple quantum well structure. With an active layer,
The semiconductor device according to claim 1, wherein the boron (B) concentration in the active layer is 1 × 10 ¹⁷ cm ⁻³ or less.

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