Peter Ersland

p-HEMT with tailored field

The high electron mobility in heterostructure devices stems from fact that electrons are injected into intrinsic layer of a semiconductor material and are confined into two-dimensional space of a heterostructure potential. However, non-linear distribution of the voltage along a transistor channel results in variation of depth and width of heterostructure potential. As in case of non-uniform electrical field in conventional field effect transistor, non-uniformity of this potential causes limitation of gain gm and operational frequency ft; increased level of noise and, most important, significantly impact the non-linearity of the gain. We illustrated our study with characteristics of tri-gate pHEMT, fabricated on M/A-COM’s high volume production AlGaAs/InGaAs process. The speed at which electrons traverse the channel was modified by providing the highest bias voltage on the first gate, and gradually decreasing the bias voltage on all subsequent gates. Thus tailored electrical field along the channel was the modeling and design base of new p-HEMTs. Manufactured devices carried in agreement with modeling, better saturation of current (large Early Voltage), significant linearity of the transconductance gm and better reliability. q 2003 Published by Elsevier Science Ltd.

ESD Protection Capabilities of GaAs Schottky Diodes

GaAs Schottky diodes varying in size from 40 mum to 400 mum anode periphery have been tested to assess their effectiveness as ESD protection devices in FET-based MMICs. ESD failure voltage is seen to increase linearly with diode size. While the capacitive loading of these diodes is too high for use in protection of most RF circuit ports, they have been shown to effectively protect sensitive DC logic circuits in E/D pHEMT switches.

Progress of quantum electronics and the future of wireless technologies

Research in quantum electronics over several decades has fueled the creation and rapid growth of todays wireless communications market. Sales of electronic components into this market exceeded

Determining DC/RF survivability limits of GaAs semiconductor circuits

25 billion in 2006. Nearly all cellular handsets sold today include integrated circuits (ICs) based on energy gap engineered transistors-high-electron mobility transistors (HEMTs) and heterojunction base transistors (HBTs). The success of these technologies notwithstanding, future wireless communications systems will require even more demanding IC performance, especially in the areas of linearity and low noise. We propose that a new concept in transistor design, wave-function engineering, offers un-tapped opportunities to realize these needed performance improvements.

Reliability investigation and characterization of failure modes in Schottky diodes

Methods for determining long term product reliability due to channel temperature, environmental conditions or bias have been thoroughly documented and understood. In contrast, intermittent DC/RF overdrive survivability limits have been looked at, but for the most part not fully understood. This is aggravated by the fact that most product datasheets only point to one absolute maximum operating value, which many times is confused with a survivability limit. This paper discusses the differences between these two distinct specifications and a method we have used for determining survivability limits based on input power and bias voltage.

Manufacturing test technologies for commercial GaAs RF/microwave integrated circuits

Schottky diodes may be realized by various techniques, depending on application and processing technology. M/A-COM has recently developed an enhancement/depletion (E/D) pHEMT process, used primarily for control circuits around its mature RF circuitry. We report here a reliability study of two diodes (configured using E-FETs), subjected to both high temperature and forward bias accelerated stress. Different failure modes observed during accelerated life tests of the two diode configurations are discussed, and the causes for aging are analyzed. Results of the stress test are backed by equivalent circuit modeling using ADS™. The differences in the effect of these failure modes on circuit performance are discussed.

Reliability validation of compound semiconductor foundry processes

The unique requirements of a production test for commercial RF/microwave IC products are described. As product cost is one of the most significant discriminators in this marketplace, techniques for minimizing the impact of test on product cost are discussed, including test system hardware, software, test plans and automated device handling. To further illustrate the impact of these techniques an example of production test for a plastic packaged single pole double throw (SPDT) switch is presented.

Lifetime acceleration model for HAST tests of a pHEMT process

Abstract An approach for assessing reliability data provided by compound semiconductor foundries is presented. This approach combines a thorough review of the foundry results with independent accelerated life tests to confirm these results. Examples are provided of cases where these independent test results did not adequately match the results provided by the foundry. Two factors are shown to be especially important: consistent temperature estimates by the foundry and the customer, and an understanding of the impact of bias conditions on the acceleration of failure mechanisms in FET and HBT technologies.