I. Definitions
As used herein, the phrase “III-nitride” or “III-N” refers to a compound semiconductor that includes nitrogen and at least one group III element including aluminum (Al), gallium (Ga), indium (In), and boron (B), and including but not limited to any of its alloys, such as aluminum gallium nitride (AlxGa(1-x)N), indium gallium nitride (InyGa(1-y)N), aluminum indium gallium nitride (AlxInyGa(1-x-y)N), gallium arsenide phosphide nitride (GaAsaPbN(1-a-b)), aluminum indium gallium arsenide phosphide nitride (AlxInyGa(1-x-y)AsaPbN(1-a-ab)), for example. III-nitride also refers generally to any polarity including but not limited to Ga-polar, N-polar, semi-polar or non-polar crystal orientations. A III-nitride material may also include either the Wurtzitic, Zincblende or mixed polytypes, and may include single-crystal, monocrystal, polycrystal, or amorphous crystal structures.
Also, as used herein, the terms “LV-device,” “low voltage semiconductor device,” “low voltage transistor,” and the like, refer to a low voltage device, with a typical voltage range of up to approximately 50 volts. Typical voltage ratings include low voltage (LV)˜0-50V, midvoltage (MV)˜50-200V, high voltage (HV)˜200-1200V and ultra high voltage (UHV)˜>1200V. The device can comprise any suitable semiconductor material that forms a field-effect transistor (FET) or diode, or a combination of a FET and a diode. Suitable semiconductor materials include group IV semiconductor materials such as silicon, strained silicon, SiGe, SiC, and group III-V materials including III-As, III-P, III-nitride or any of their alloys.
II. Background Art
III-nitride materials are semiconductor compounds that have a relatively wide, direct bandgap and potentially strong piezoelectric polarizations, and can enable high breakdown fields, high saturation velocities, and the creation of two-dimensional electron gases (2-DEGs). As a result, III-nitride materials are used in many power applications such as depletion mode (e.g., normally ON) power field-effect transistors (power FETs), high electron mobility transistors (HEMTs), and diodes.
In power management applications where normally OFF characteristics of power devices are desirable, a depletion mode III-nitride power transistor can be cascoded with a low voltage (LV) semiconductor device to produce an enhancement mode composite power device. However, the utility and durability of such a composite device can be limited according to characteristics of the III-nitride power transistor and LV semiconductor device being used in combination. For example, when implemented with an LV semiconductor device to form a composite device used in high current applications, the gate of the III-nitride power transistor may tend to oscillate when configured in series with semiconductor package inductances and the output capacitance of the LV semiconductor device, for example, causing the ITT-nitride power transistor to be undesirably turned OFF and ON. Unless, controlled and dampened, such oscillations may adversely affect the functionality and utility of the composite semiconductor device, and can also be destructive and reduce the durability of the composite semiconductor device.