High-breakdown-voltage Ga/sub 0.51/In/sub 0.49/P channel MESFET's grown by GSMBE
The first Ga/sub 0.51/In/sub 0.49/P channel MESFETs grown on a (100) GaAs substrate by GSMBE have been fabricated. A high gate-to-drain breakdown voltage of 42 V with a high maximum current density (320 mA/mm) was achieved. This result demonstrates that high-breakdown voltage could be attained by using Ga/sub 0.51/In/sub 0.49/P as the channel material. We also measured a high-maximum oscillation frequency (f/sub max/) of 30 GHz for a 1.5 /spl mu/m gate-length device. This value is quite high compared with other high-breakdown-voltage GaAs MESFET's or MISFET's with the same gate length.
High-Linearity High-Current-Drivability Gao.5 1 Ino.49P/GaAs MISFET Using Gao.5 1 Ino.49P Airbridge Gate Structure Grown by GSMBE
A novel structure Gao.51 Im.rsP/GaAs MISFET with an undoped Gao.slIno.*eP layer serving as the airbridge between active region and gate pad was first designed and fabricated. Wide and flat characteristics of gm and f max versus drain current or gate voltage were achieved. The device also showed a very high maximum current density (610 mA/mm) and a very high gate-to-drain breakdown voltage (25 V). Parasitic capacitances and leakage currents were minimized by the air- bridge gate structure and thus high f~ of 22 GHz and high f,,, of 40 GHz for 1 pm gate length devices were attained. To our knowledge, both were the best reported values for 1 pm gate GaAs channel FET's.
Exposure to violence in incarcerated youth from the city of São Paulo.
OBJECTIVE
This study aimed to determine the extent of exposure to community violence among delinquent Brazilian youth in the 12-month period prior to their incarceration and to identify factors associated with this exposure.


METHOD
With an oversampling of girls, a cross-section of youth under 18 years of age from juvenile detention units in the city of São Paulo, Brazil completed a structured interview. Key items related to exposure to violence (witnessed and experienced) were drawn from the Social and Health Assessment questionnaire to cover the 12-month period prior to incarceration.


RESULTS
Participants (n = 325, 89% boys) reported high rates of exposure to violence with largely similar levels for boys and girls. Being threatened with physical harm, being beaten or mugged and/or shot at were the most common forms of violence experienced. After controlling for demographic and family variables, the fact of having peers involved in risk behavior, easy access to guns and previous involvement with the justice system were associated with witnessed violence; whereas having slept on the street was the only variable associated with experienced violence.


CONCLUSION
This group of youth was exposed to high levels of violence and other adverse experiences. Future research should examine the effectiveness of strategies aimed at reducing the exposure to violence of high-risk youth.