Discrete Transistors Market

The term "discrete" refers to a packaged semiconductor device having a single "device", an electrical functional component such as a diode, transistor, or thyristor. These devices must be combined with other components to provide a basic electrical function such as amplification, switching, or latching.

The discrete product area and its players have always been viewed as the "stable" semiconductor product. Transistors are three terminal devices in which two of the terminals provide the normal current path and the third represents the controlling electrode. This control electrode allows the transistor to amplify signals (analog mode) or to operate as a current switch (digital mode).

The two main types of transistors are bipolar transistors and field-effect transistors (FETs). Bipolar transistors have a "base" electrode, which allows a small current to control a larger current between the "emitter" and "collector" electrodes.

The FET differs in that a voltage at the gate electrode controls current flow between the source and drain electrodes. Power transistors are devices that can control 1A or more of current, can dissipate 1 or more watts of power, or are capable of operating with voltages exceeding 50V.

Power transistors are used in applications as switch-mode power supplies, power inverters, regulators, and motor controls. Power transistor applications have been dominated by bipolar devices. However, in the past decade, the power MOSFET device has become prevalent in applications involving high-speed switching.

In power-switching applications, the range above 1,000V is still well-dominated by the bipolar power transistor, but power MOSFETs have become competitive in the 100V-to-600V range.

Worldwide Discrete Power Transistor Revenue (billions of Dollars)

PRESENTLY, THE MARKET IS DOMINATED BY SILICON, WHICH IN MANY RESPECTS HAVE REACHED ITS PERFORMANCE LIMIT AND IS NOT ABLE TO SATISFY THE GROWING REQUIREMENTS OF POWER SUPPLY DESIGNERS, E.G. TO PROVIDE HIGHER EFFICIENCY, HIGHER CURRENT DENSITY, HIGHER FREQUENCY, HIGHER OPERATION TEMPERATURE, ETC.

GaAs High-Voltage, High-Frequency, High-Temperature Power Heterojnction Bipolar Transistor (PHBT)

Figure1a.
3D fragment of the GaAs Power Heterojunction Bipolar p-n⁺-n-i-p-p⁺ transistor.

Development of the transistors is based on a novel Liquid Phase Epitaxial (LPE) growth technique which facilitates the rapid growth of GaAs positive-intrinsic-negative (p-i-n) structures which have a thick i-region with extremely low impurity concentration (less than 10¹¹cm^-3) making them suitable for high-voltage (up to 1000 Volts) and high-temperature (up to 300°C) operation.

A p-i-n layer structure can be used to fabricate a high-voltage, high-temperature, high-frequency power p⁺-p-n⁺-i-p-⁺ transistor with wide-gap emitter ( Fig. 1a,b,c). Cross-section of such transistor is shown schematically in Fig.2, 3

Fig.1b Optical microphotography of 12x12 mm wafer with 16 transistor patterns	Fig.1c Low-magnification SEM photo of one of 16 ready transistor patterns on 12x12 mm wafer

Figure2

• a)- Schematic diagram of a p-n-i-p bipolar transistor with
  
  wide-gap emitter
• b)- Collector depletion region field

• 1.-p⁺-substrate
• 2.-collector p-region
• 3.-collector i-region
• 4.-collector-base n-region
• 5.-base n⁺-region
• 6.-emitter AlGaAs p-region
• 7.-p⁺-region

Here the p-i-n layer structure is grown by liquid phase epitaxy (LPE) on a p⁺-substrate. After removing most of the n layer by polishing leaving a thin n-region adjacent to i-region, thin and heavily-doped n+-base, AlGaAs p-emitter and p⁺-contact layer are grown by metal-organic vapor phase epitaxy (MOVPE) (See Fig.3)

Figure3.
SEM image of the MOVPE GaAs:Si, AlGaAs, GaAs:Zn layers on LPE pre grown and polished p⁺(111B)- p-i-n structure

Performance,Advantages and Aplications

These novel HIGH TEMPERATURE, HIGH FREQUENCY, HIGH VOLTAGE GaAs Power Bipolar Heterojunction Transistors represent a new generation of active semiconductor components for applications requiring up to 600 Volts blocking voltage, working currents up to 30 Amperes, frequency up to 5000MHz, operating temperature up to 250ºC.
The inherent physical properties of GaAs, coupled with basic physics high-voltage P⁺-P-i -N⁺-P heterostructure yield transistors with parameters superior to silicon.

RF Power Bipolar Transistors (market size more than $1 Billion)

Figure 4.
Estimated GaAs RF Heterojunction Bipolar Transistor in comparison with producible
Silicon RF Power Bipolar Transistors

Estimated main advantages of the GaAs Power Heterojunction Bipolar Transistors

• High load power
• High blocking voltage
• High maximum operating junction temperature
• High frequency
• High current gain parameter
• High linearity
• High efficiency
• Low switching times and power losses
• Current gain weakly depends on current
• Temperature independent dynamic characteristics
• High radiation hardness

Some of Applications of the GaAs Power Heterojunction Bipolar Transistors

• Avionics
• L and S -Band Radars
• Cellular (Wireless) Base Station
• Broadcast
• Military and Communication Transmitters
• Microwave Oven (in particular instead of the magnetron)
• HF DC/AC inverters and HF DC to DC converters
  
  (in particular electric drive for electric or hybrid automotive vehicles)
• High temperature electric drive for oil drilling

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