GaN HEMT (High Electron Mobility Transistor) power device with diode for regulating and controlling substrate voltage
By introducing diodes to regulate the substrate voltage in GaN HEMT power devices, the problem of dynamic on-resistance degradation caused by substrate charge accumulation is solved, achieving high withstand voltage and improved stability, while remaining compatible with existing processes.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NANJING UNIV OF POSTS & TELECOMM
- Filing Date
- 2026-02-13
- Publication Date
- 2026-05-12
AI Technical Summary
In high-voltage switching applications, GaN HEMT power devices are prone to electron capture when the substrate is at a high potential in the off state, which leads to the accumulation of net negative charge in the buffer layer, degradation of dynamic on-resistance, and affects the switching stability and reliability of the device.
A diode is connected between the substrate and ground, and the substrate is connected to the floating field plate through a metal line. An isolation region is set between the drain and the diode region. The substrate voltage is clamped by the diode to provide a charge discharge path and suppress the degradation of dynamic on-resistance.
While maintaining high withstand voltage, it suppresses the degradation of dynamic on-resistance, improves the switching stability and reliability of the device, and is compatible with conventional processes.
Smart Images
Figure CN122028495A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of power semiconductor technology and relates to a GaN HEMT power device with diode-controlled substrate voltage. Background Technology
[0002] As a third-generation wide-bandgap semiconductor, GaN possesses advantages such as a wide bandgap, high critical breakdown field strength, and high electron mobility, making it suitable for high-power and high-frequency devices. Conventional GaN HEMT power devices form a high-density two-dimensional electron gas (2DEG) through spontaneous polarization and piezoelectric polarization effects, thereby achieving low on-resistance and high current density. However, in high-voltage switching applications, GaN HEMT power devices typically withstand high drain voltages in the off-state, triggering electron trapping in the buffer layer, especially when the substrate is at a high potential. The buffer layer is more likely to trap electrons and accumulate net negative charge on the substrate. When the device switches from the off-state to the on-state, the charge accumulated in the substrate and buffer layer is difficult to release, leading to degradation of dynamic on-resistance and reducing the switching stability and reliability of the device. Although B. Li et al. proposed in their paper "900V Normally-OFF GaN-on-Si Transistors Achieved by Substrate Potential Modulation (SPM)" to achieve high breakdown voltage and suppress dynamic resistance degradation by integrating a main transistor and a substrate-connected MOS transistor to modulate the substrate potential. However, the integrated MOSFET in this structure increases the gate input capacitance of the device, increasing the load loss of the gate drive circuit. Patent application CN119835964A discloses a substrate voltage-controlled GaN HMET power device, which connects the substrate to a floating field plate in a metal connection. By utilizing the high potential of the field plate under high drain voltage, the substrate potential is raised, thereby assisting in the depletion of the drift region and improving the device's breakdown voltage without increasing drive losses. However, the increase in substrate potential in this structure causes the substrate to accumulate negative charges, leading to dynamic resistance degradation. Summary of the Invention
[0003] To address the aforementioned problems, this invention proposes a GaN HEMT power device with diode-controlled substrate voltage. By connecting a diode between the substrate and ground, substrate clamping is achieved, which maintains high withstand voltage while suppressing dynamic on-resistance degradation, improving switching stability, and has a simple structure and is compatible with various processes.
[0004] This invention discloses a GaN HEMT power device with diode-controlled substrate voltage, comprising, from bottom to top along the vertical direction of the device, a substrate, a GaN buffer layer, a GaN channel layer, an AlGaN barrier layer, a passivation layer, and a floating field plate structure; along the lateral direction of the device, the device surface has, from one side to the other, a first conductive material, a gate structure, a third conductive material, a fourth conductive material, and a fifth conductive material that do not contact each other; the lower end of the first conductive material penetrates the passivation layer and contacts the barrier layer, forming an ohmic contact, and the upper surface of the first conductive material leads out a source electrode, which is grounded; the lower end of the third conductive material penetrates the passivation layer and contacts the barrier layer, forming an ohmic contact, and the upper surface of the third conductive material leads out a drain electrode; the fourth conductive material penetrates the barrier layer and contacts the upper surface of the channel layer, forming an ohmic contact; the fifth conductive material penetrates the barrier layer and contacts the upper surface of the channel layer, forming a Schottky contact; the gate structure includes a second conductive material and a first P-type GaN layer, with the gate electrode leading out from the upper surface of the second conductive material; The third conductive material and the fourth conductive material have an isolation region that extends vertically to the substrate surface; the substrate and the floating field plate structure are connected by a first metal; a diode is connected between the substrate and ground; a diode cathode is led out from the upper surface of the fourth conductive material; the diode cathode is connected to the substrate by the first metal; a diode anode is led out from the upper surface of the fifth conductive material; and the diode anode is connected to the source by a second metal.
[0005] Furthermore, the diode is a PN junction diode, which includes a second P-type GaN layer disposed below the fifth conductive material. The second P-type GaN layer forms a PN junction with the AlGaN barrier layer and the GaN channel layer, and the fifth conductive material forms an ohmic contact with the second P-type GaN layer.
[0006] Furthermore, the lower ends of the first conductive material and the third conductive material penetrate the barrier layer and extend into the GaN channel layer, and their lower surfaces form an ohmic contact with the GaN channel layer.
[0007] Furthermore, the isolation region is either ion implantation isolation or trench isolation.
[0008] Furthermore, the isolation zone is isolated by trenches and filled with a passivation layer.
[0009] Furthermore, the substrate material is silicon, silicon carbide, sapphire, or GaN.
[0010] The beneficial effects of this invention are as follows: This invention connects the substrate to the field plate via a metal wire and connects a diode between the substrate and ground, while simultaneously providing an isolation region between the drain and the diode region; the diode anode is grounded and the cathode is connected to the substrate. When the device is in a blocking state, the isolation region prevents the high voltage from the drain from laterally penetrating to the diode region, and the substrate remains at a high potential, assisting in the depletion of the drift region, while the substrate also accumulates net negative charge; when conducting, the substrate potential is clamped to the diode's forward voltage, while providing a discharge path for the net negative charge accumulated on the substrate, promoting rapid charge release, suppressing dynamic on-resistance degradation, improving device stability, and the device structure is simple and compatible with conventional processes. Attached Figure Description
[0011] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the structure of Embodiment 3 of the present invention; Figure 4 This is a breakdown characteristic curve of Embodiment 2 of the present invention and a conventional GaN HEMT; Figure 5 This is a comparison chart of the normalized on-resistance of Embodiment 2 of the present invention, a conventional GaN HEMT, and a GaN HEMT without a connected diode. Wherein, 1-substrate 1, 2-GaN buffer layer, 3-GaN channel layer, 4-AlGaN barrier layer, 5-first P-type GaN layer, 61-first conductive material, 62-second conductive material, 63-third conductive material, 64-fourth conductive material, 7-passivation layer, 8-floating field plate structure, 9-first metal, 10-second metal, 11-isolation region, 12-second P-type GaN layer. Detailed Implementation
[0012] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.
[0013] Example 1
[0014] like Figure 1As shown, the present invention discloses a GaN HEMT power device with diode-controlled substrate voltage, comprising, from bottom to top along the vertical direction of the device, a substrate 1, a GaN buffer layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, a passivation layer 7, and a floating field plate structure 8; along the lateral direction of the device, the device surface has, from one side to the other, a first conductive material 61, a gate structure, a third conductive material 63, a fourth conductive material 64, and a diode anode structure that are not in contact with each other; the lower end of the first conductive material 61 penetrates the passivation layer and contacts the barrier layer 4, forming an ohmic contact, and the upper surface leads out the source electrode; the lower end of the third conductive material 63 penetrates the passivation layer and contacts the barrier layer 4, forming an ohmic contact, and the upper surface leads out the drain electrode; the fourth conductive material 64 contacts the upper surface of the barrier layer 4, forming an ohmic contact, and the upper surface leads out the diode cathode; wherein, the gate structure includes a second conductive material 62 and a first P The diode comprises a fifth conductive material 65 and a second P-type GaN layer 12, the second P-type GaN layer 12 forming a PN junction with the AlGaN barrier layer 4 and the GaN channel layer 3. The fifth conductive material 65 forms an ohmic contact with the second P-type GaN layer 12, and the diode anode is led out from its upper surface. An isolation region 11 is provided between the third conductive material 63 and the fourth conductive material 64. The isolation region 11 extends vertically to the surface of the substrate 1. The isolation region 11 is isolated by trenches and filled with a passivation layer 7. The substrate 1 is connected to the floating field plate structure 8 through a first metal 9. The diode is connected between the substrate 1 and ground. The cathode of the diode is connected to the substrate 1 through the first metal 9, and the anode and source of the diode cathode are connected through a second metal 10.
[0015] The working principle of this example is as follows:
[0016] The device connects the substrate to the field plate via a metal wire and a diode to ground. An isolation region is provided between the drain and the diode region. The diode anode is grounded and the cathode is connected to the substrate. When the device is in the blocking state, the isolation region prevents the high voltage from the drain from laterally penetrating to the diode region, and the substrate remains at a high potential, assisting in the depletion of the drift region. At the same time, the substrate also accumulates net negative charge. When the device is in the conducting state, the substrate potential is clamped to the diode's on-state voltage, while providing a discharge path for the net negative charge accumulated on the substrate, promoting rapid charge release, suppressing dynamic on-resistance degradation, and improving device stability.
[0017] Example 2
[0018] like Figure 2As shown, the difference between this example and Example 1 is that this example features a GaN HEMT power device with substrate clamping function. The diode is a Schottky diode, and the lower end of the fifth conductive material penetrates the barrier layer and contacts the channel layer. This contact is a Schottky contact, and the diode anode is led out from the upper surface. Compared to Example 1, the advantages of this example are that the Schottky diode has a lower barrier, the substrate potential is clamped to a higher diode turn-on voltage, and the dynamic resistance on-resistance degradation suppression effect is better.
[0019] Example 3
[0020] like Figure 3 As shown, the difference between this example and Example 2 is that in this example, the GaN HEMT power device with substrate clamping function has its lower ends penetrating the barrier layer and extending into the channel layer, with its lower surface forming an ohmic contact with the channel layer. Compared to Example 2, the advantage of this example is that the lower ends of the first and third conductive materials are in direct contact with the channel layer, reducing contact resistance and improving the device's conductivity.
[0021] Figure 4 This is a comparison of the breakdown characteristics of Example 2 obtained from simulation with those of a conventional GaN HEMT. For example... Figure 4 As shown, the breakdown voltage of Example 2 is 1225V, while the breakdown voltage of a conventional GaN HEMT is 363V. Figure 4 As shown, the pressure resistance of Example 2 is significantly improved.
[0022] Figure 5 To compare the normalized on-resistance of Example 2 obtained from simulation with that of a conventional GaN HEMT and a GaN HEMT without a connected diode, under a high drain voltage of 200V, the normalized on-resistance of the HEMT structure without a connected diode is 2.66, the normalized on-resistance of Example 2 is 1.26, and the normalized on-resistance of the conventional GaN HEMT is 1.38. Figure 5 As shown, the dynamic performance of the structure proposed in this invention is significantly improved, indicating that the introduction of the diode significantly suppresses the increase in dynamic on-resistance.
[0023] The above description is merely a preferred embodiment of the present invention and is not intended to further limit the present invention. All equivalent changes made based on the description and drawings of the present invention are within the protection scope of the present invention.
Claims
1. A GaN HEMT power device with diode-controlled substrate voltage, comprising, in the vertical direction of the device, a substrate (1), a GaN buffer layer (2), a GaN channel layer (3), an AlGaN barrier layer (4), a passivation layer (7), and a floating field plate structure (8) stacked sequentially from bottom to top; in the lateral direction of the device, the device surface has, from one side to the other, a first conductive material (61), a gate structure, a third conductive material (63), a fourth conductive material (64), and a fifth conductive material (65) that do not contact each other; the lower end of the first conductive material (61) penetrates the passivation layer (7) and contacts the barrier layer (4), the contact being an ohmic contact, and the first conductive material... The source electrode is drawn out from the upper surface of the material (61), and the source electrode is grounded; the lower end of the third conductive material (63) penetrates the passivation layer (7) and contacts the barrier layer (4), and the contact is an ohmic contact, and the drain electrode is drawn out from the upper surface of the third conductive material (63); the fourth conductive material (64) penetrates the barrier layer (4) and contacts the upper surface of the channel layer (3), and the contact is an ohmic contact; the fifth conductive material (65) penetrates the barrier layer (4) and contacts the upper surface of the channel layer (3); the gate structure includes a second conductive material (62) and a first P-type GaN layer (5), and the gate electrode is drawn out from the upper surface of the second conductive material (62); Its features are, An isolation region (11) is provided between the third conductive material (63) and the fourth conductive material (64), and the isolation region (11) extends to the surface of the substrate (1) in a vertical direction; The substrate (1) is connected to the floating field plate structure (8) through a first metal (9); a diode is connected between the substrate (1) and the ground; a diode cathode is led out from the upper surface of the fourth conductive material (64); the diode cathode is connected to the substrate (1) through the first metal (9); the fifth conductive material (65) is in contact with the channel layer (3) as a Schottky contact; a diode anode is led out from the upper surface of the fifth conductive material (65); and the diode anode is connected to the source through a second metal (10).
2. The GaN HEMT power device with diode-controlled substrate voltage according to claim 1, characterized in that, The diode is a PN junction diode, which includes a second P-type GaN layer (12) disposed below the fifth conductive material (65). The P-type GaN layer (12) forms a PN junction with the AlGaN barrier layer (4) and the GaN channel layer (3), and the fifth conductive material (65) forms an ohmic contact with the second P-type GaN layer (12). The anode of the diode is led out from the upper surface of the fifth conductive material (65).
3. A GaN HEMT power device with diode-controlled substrate voltage according to claim 1, characterized in that, The lower ends of the first conductive material (61) and the third conductive material (63) penetrate through the barrier layer (4) and extend into the GaN channel layer (3), and the lower surface forms an ohmic contact with the GaN channel layer (3).
4. A GaN HEMT power device with diode-controlled substrate voltage according to claim 1, characterized in that, The isolation region (11) is either ion implantation isolation or trench isolation.
5. A GaN HEMT power device with diode-controlled substrate voltage according to claim 4, characterized in that, The isolation zone (11) is isolated by trenches and filled with a passivation layer (7).
6. A GaN HEMT power device with diode-controlled substrate voltage according to claim 1, characterized in that, The substrate (1) material is silicon, silicon carbide, sapphire or GaN.