CN105870165A - InAlN/GaN HEMT device comprising barrier layer with gradually varied components - Google Patents

Abstract

The invention discloses an InAlN/GaN HEMT device with gradually changing components of the barrier layer. The device includes a GaN nucleation layer, a GaN buffer layer, an AlN insertion layer, an InAlN barrier layer with a graded In composition, a GaN cap layer, a SiN passivation layer, and gate and source electrodes formed on the substrate material in sequence. And the drain, which is characterized by the underlying In _0.17 Al _0.83 N barrier and the GaN material to form a lattice match, by increasing the In composition layer by layer, increasing the two-dimensional electron gas concentration generated by the polarization effect, and improving the saturation current and output of the device power. The invention effectively improves the electrical performance of the InAlN/GaN HEMT device while reducing the formation of linear dislocations at the heterogeneous interface and suppressing the inverse piezoelectric effect.

Description

A InAlN/GaN HEMT Device with Gradient Barrier Layer Composition

technical field

The invention relates to the field of manufacturing semiconductor power devices, in particular to an InAlN/GaN HEMT device with a gradient composition of a barrier layer.

Background technique

Compared with traditional narrow-bandgap semiconductors, wide-bandgap III-nitride semiconductors represented by GaN have superior electrical properties such as high breakdown electric field, high electron saturation velocity, and high thermal stability. In particular, the AlGaN/GaN heterojunction with significant piezoelectric and spontaneous polarization effects can induce a high concentration of two-dimensional electron gas (2DEG) at the interface, which is the core structure of HEMT. At present, the cut-off frequency of the reported AlGaN/GaN HEMT exceeds 100GHz, and the maximum output power is close to 10W/mm. However, due to the lattice mismatch between AlGaN and GaN materials, a large number of linear dislocations will be introduced during the material growth process, resulting in device leakage current much larger than the theoretical value. Many studies on the reverse leakage current of the AlGaN/GaN HEMT gate point out that the linear dislocation between heterointerfaces is the main transport channel of the leakage current. In addition, the inverse piezoelectric effect caused by lattice mismatch is also considered to be the main cause of many reliability problems of AlGaN/GaN HEMTs. Therefore, reducing the linear dislocations formed at the heterointerface and suppressing or even eliminating the inverse piezoelectric effect of the barrier layer are very important to improve device performance.

At present, one of the most effective solutions is to directly grow a lattice-matched In _0.17 Al _0.83 N barrier layer on the GaN epitaxial wafer. Although there is no piezoelectric polarization effect, its strong spontaneous polarization can also induce a large number of 2DEGs at the heterointerface, providing a large saturation current and output power. However, studies have shown that changes in the composition of barrier layer materials can significantly affect the 2DEG concentration induced by the heterointerface. The level of 2DEG concentration directly affects the saturation current and output power of the formed device. However, the lattice matching structure with fixed composition fixes the In composition of the barrier layer at 0.17, and the 2DEG concentration obtained by this composition is not the highest. It is clear that the component-fixed lattice-matched structure is suboptimal in terms of partial electrical performance of the device in order to achieve lattice matching.

The object of the present invention is to provide an InAlN/GaN HEMT device with a gradient composition of the barrier layer for the deficiencies in the prior art. Realize the lattice matching between the underlying In _0.17 Al _0.83 N barrier and the GaN material, reduce the formation of linear dislocations at the heterogeneous interface, and suppress the inverse piezoelectric effect, and at the same time enhance the spontaneous polarization effect by increasing the In composition of other layer barriers The concentration of 2DEG increases the saturation current and output power of the device. The device structure improves the saturation current and output power of the device while reducing the linear dislocation formed by the heterogeneous interface and suppressing the inverse piezoelectric effect. Not only the reliability of the device is considered, but also the electrical performance of the device is improved.

Contents of the invention

In view of the deficiencies in the prior art, the object of the present invention is to provide an InAlN/GaN HEMT device with a gradient composition of the barrier layer, which uses the underlying In _0.17 Al _0.83 N barrier to achieve lattice matching with the GaN material. Increase the In composition of the barrier layer, increase the concentration of 2DEG generated by the polarization effect, and increase the saturation current and output power of the device.

The present invention realizes through following technical scheme:

In order to achieve the above object, the present invention provides an InAlN/GaN HEMT device with a gradually changing composition of the barrier layer, which mainly includes a GaN nucleation layer, a GaN buffer layer, an AlN insertion layer, and a gradually changing In composition on the substrate material. InAlN barrier layer, GaN cap layer, passivation layer and gate, source and drain formed thereon. In this structure, the substrate material is Si, SiC, sapphire or GaN; the thickness of the GaN nucleation layer is 30nm; the GaN buffer layer is unintentionally doped with a thickness of 3μm; the thickness of the AlN insertion layer is 5nm; - 6 layers, each layer thickness is 2-5nm. The In composition of the bottom barrier layer is 0.17, which realizes lattice matching with GaN, and the In composition of the remaining barrier layers gradually increases, and the composition of the top layer does not exceed 0.32, for example: 0.17, 0.20, 0.23, 0.26, 0.29, 0.32; GaN cap The layer thickness is 2nm; the passivation layer is SiN, SiO ₂ , or Si ₃ N ₄ , with a thickness of 150nm; the source and drain are ohmic contact metals using Ti/Al/Ti/Au, with a thickness of 30nm, 120nm, and 50nm, respectively. 100nm; the gate metal is Ni/Au, the thicknesses are 50nm and 300nm respectively;

In the InAlN/GaN HEMT device with a gradient composition of the barrier layer provided by the present invention, the underlying In _0.17 Al _0.83 N barrier realizes lattice matching with the GaN material, effectively reducing the linear dislocation formed at the heterogeneous interface during the material growth process, At the same time, the inverse piezoelectric effect at the heterointerface is suppressed. On the premise of ensuring the reliability of the device, the saturation current and output power of the device are further improved by gradually changing the composition of the barrier layer In. The invention has important significance for the preparation of GaN-based HEMT devices and the improvement of their electrical properties.

Description of drawings

Fig. 1 is a schematic diagram of the layer structure of an InAlN/GaN HEMT device with a gradient composition of the barrier layer of the present invention;

Figure 2 is a schematic diagram of the layer structure of an InAlN/GaN HEMT device with a fixed barrier layer composition;

Figure 3 is the I _d -V _g curves of two InAlN/GaN HEMT devices with barrier layer composition gradient and fixed composition;

Figure 4 is the I _d -V _d curves of two InAlN/GaN HEMT devices with barrier layer composition gradient and fixed composition.

detailed description

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings and embodiments.

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

The InAlN/GaN HEMT device with a graded barrier layer composition provided by the present invention comprises a GaN nucleation layer, a GaN buffer layer, an AlN insertion layer, an InAlN barrier layer with a graded In composition, and a GaN Cap layer, passivation layer and gate, source and drain formed thereon.

The schematic diagram of the InAlN/GaN HEMT device layer structure with the barrier layer composition gradient is shown in Figure 1. The substrate material is Si, SiC, sapphire or GaN; the thickness of the GaN nucleation layer is 30nm; the GaN buffer layer is unintentionally doped with a thickness of 3μm; the thickness of the AlN insertion layer is 5nm; the InAlN barrier is divided into 3-6 layers, The thickness of each layer is 2-5nm. The In composition of the bottom barrier layer is 0.17, which realizes lattice matching with GaN, and the In composition of the remaining barrier layers gradually increases, and the composition of the top layer does not exceed 0.32, for example: 0.17, 0.20, 0.23, 0.26, 0.29, 0.32; GaN cap The layer thickness is 2nm; the passivation layer is SiN, SiO ₂ , or Si ₃ N ₄ , with a thickness of 150nm; the source and drain are ohmic contact metals using Ti/Al/Ti/Au, with a thickness of 30nm, 120nm, and 50nm, respectively. 100nm; the gate metal is Ni/Au, and the thicknesses are 50nm and 300nm respectively; the schematic diagram of the InAlN/GaN HEMT device layer structure with a fixed barrier layer composition is shown in Figure 2, and the barrier layer In composition is fixed, and the thickness is 30nm. The preparation process is to gradually grow a GaN nucleation layer, a GaN buffer layer, an AlN insertion layer, an InAlN barrier layer with a gradient In composition, and a GaN cap layer on the substrate material by metal-organic chemical vapor deposition. The evaporation process defines the electrode structure, and finally a passivation layer is grown to reduce the surface lateral leakage current. It is worth noting that changes in the In composition and thickness of the barrier layer have certain effects on the concentration of 2DEG. The concentration of 2DEG induced by the polarization effect also increases with the increase of In composition and thickness of the barrier layer. However, if the composition is too large, the strain relaxation of the barrier layer will be caused, which will deteriorate the material properties of the heterojunction. Therefore, the composition and thickness of the barrier layer of the present invention need to be controlled within the range of less than 0.32 nm and less than 30 nm, respectively. In addition, barrier layer composition and thickness control can achieve higher 2DEG mobility values. This is because when the composition and thickness of the barrier layer increase, the 2DEG density will increase, the distribution will narrow, and it will be closer to the heterointerface, resulting in changes in various scattering effects, which will instead reduce the 2DEG concentration. Under the same conditions, compared with the InAlN/GaN HEMT device with fixed composition, the barrier layer composition gradient InAlN/GaN HEMT proposed by the present invention has a larger saturation current, and its output power is higher (as shown in Figures 3 and 4 Show).

The present invention adopts the underlying In _0.17 Al _0.83 N barrier to realize lattice matching with GaN materials, and increases the saturation current and output by gradually increasing the In composition of the barrier layer and enhancing the 2DEG concentration induced by the spontaneous polarization effect of the heterogeneous interface. power, which improves the electrical performance of InAlN/GaN HEMTs. Therefore, the structure is helpful for the preparation of GaN-based power devices and the improvement of their electrical performance. For AlGaN/GaN HEMT devices, the linear dislocations at the heterointerface and the inverse piezoelectric effect caused by lattice mismatch seriously affect the reliability of their work. However, for In _0.17 Al _0.83 N/GaN HEMTs that have achieved lattice matching, since the In composition is fixed at 0.17, there is room for further improvement in its electrical performance. In the present invention, the electrical performance of the InAlN/GaN HEMT is further improved by using the underlying In _0.17 Al _0.83 N barrier to realize lattice matching with the GaN material, and gradually increasing the In composition of the barrier layer. At the same time, the change of In composition in each layer is controlled to be small, the linear dislocation formed between the barrier layers is reduced and the inverse piezoelectric effect is suppressed. By controlling the In composition of the barrier layer and the thickness of the barrier layer respectively, the best electrical performance. Compared with the prior art, the present invention has the following beneficial effects: on the premise of ensuring the reliability of the device, by gradually changing the composition of the barrier layer In, the saturation current and output power of the device are further improved.

Finally, it is noted that the above embodiments are only used to illustrate the technical solutions of the present invention without limitation. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be carried out Modifications or equivalent replacements without departing from the spirit and scope of the technical solution of the present invention shall be covered by the claims of the present invention.

Claims (5)

1. A barrier layer composition graded InAlN/GaN HEMT device, characterized in that: the device comprises a GaN nucleation layer formed sequentially on the substrate material, a GaN buffer layer, an AlN insertion layer, and an In composition graded InAlN potential Barrier layer, GaN cap layer, passivation layer and gate, source and drain formed thereon. 2 . The InAlN/GaN HEMT device with graded barrier layer composition according to claim 1 , wherein the substrate material is Si, SiC, sapphire or GaN. 3. The InAlN/GaN HEMT device with gradual barrier layer composition according to claim 1, characterized in that the InAlN barrier is divided into 3-6 layers, each layer thickness is 2-5nm, and the total thickness is 18nm-30nm within range. 4. The InAlN/GaN HEMT device according to claim 1, wherein the composition of the barrier layer is graded, wherein the In composition of the underlying barrier layer is 0.17 to achieve lattice matching with GaN, and the In composition of the remaining barrier layers is 0.17. Gradually increase, the top component does not exceed 0.32, for example: 0.17, 0.20, 0.23, 0.26, 0.29, 0.32. 5 . The InAlN/GaN HEMT device with graded barrier layer composition according to claim 1 , wherein the passivation layer is SiN, SiO ₂ , or Si ₃ N ₄ .