INTERNATIONAL ELECTRON DEVICES ANNUAL MEETING 433

increases in output power that were depen- dent on the initial fill pressure of COZ. The system was also filled with a COt-He mixture and made to lase. Heating of the platinum wire caused a decrease in output power. I t was tentatively concluded that the platinum catalyzes the reaction CO+O+COz, per- mitting a higher concentration of COz In a sealed system than is otherwise possible.

4) Long-Life Static-Gas C02-He Laser- E'. T. Whitney and W. J . Graham, Naval Research Laboratory, Washington, D . C. We have obtained a lifetime in excess of

1100 hours on one gas fill of a static-gas C'CV C02-He laser. The Brewster window tube, which has a 92-cm discharge length and a 10-mm ID, produced an output power of 1.4 watts (within 10 percent) throughout this period, and showed no indication of decreas- ing when the test was arbitrarily terminated. From this and other life-test data to be re- ported, the long life is attributed to exclu- sion of nitrogen, careful vacuum technique and outgassing procedure, and dc electrodes which minimize hot spots and sputtering. In all our tests addition of nitrogen to CO2 and to COz plus He caused short lifetimes and reduced output power except in the first few seconds. The partial pressure of CO2 was measured by condensing it in a cold finger a t 77°K. After 1100 hours of continuous opera- tion, a measurement of the COZ partial pres- sure showed that only 15 percent of the COS gas fill was undissociated. The low efficiency (1 percent) of this tube is due to the high absorption loss in the Irtran 2 windows, which, however, are nonhygroscopic and thus useful for life-test data.

5 ) 20-Watt Single-Frequency CO, Laserg6- R. S. Reynolds, Sylvania Electronic Sys- tems, Mountain View, Calif . and J . D . Schlafer, Geneva1 Telephone & Elec- tronics Labs., Bayside, N . Y. A short-term frequency-stabilized, single-

frequency, sealed-off COZ laser is described which is capable of emitting 20 watts in a single mode. The technique used to obtain both high power and high frequency stabil- ity simultaneously utilizes a master oscil- lator-power amplifier approach. The oscil- lator consists of a 3 to 5 watt, 1-meter-long Brewster-angle laser. Single-wave-length operation is obtained by length-tuning the laser. Heterodyne measurements on two os- cillator units have indicated short-term stabilities of better than 1 : 1OQ (30 kHz) in a normal laboratory environment. Instabil- ities are primarily due to atmospheric pres- sure fluctuations, airborne vibrations due to laboratory noise and vibrations from the cooling water used with the lasers. Long- term frequency stabilities of about 1: 107 (3 illHz) have been obtained by thermal control techniques alone. The amplifier re- quired to increase the laser power to 20 watts consists of two dc-operated 2-meter- long tubes with Brewster windows. The de- sign and operating characteristics of the laser are given with up-to-date performance results.

Space Flight Center, Greenbelt, Md., under Contract This work was supported by NASA Goddard

NAS-10309.

6 ) Proposed Ultrastable COZ OscillatorQ7- P . Rabinowitz, J . T . LaTouvrette, and G. Gould, Polytechnic Institute of Brook- lyn, Farmingdale, N . Y . Stabilized gas laser systems have failed

to achieve the ideal stability, determined by fundamental noise, by as much as five orders of magnitude. Regardless of tech- niques used, long-term stability has been limited by changes in discharge parameters affecting the center frequency of the spec- tral line used as the reference. The most serious causes of instability are the changes in gas density, composition, temperature, and electron density which are difficult t o avoid in a gas discharge.

\Ye believe that a significant improve- ment in stability can be achieved through the use of a passive, thermally excited refer- ence cell, thereby avoiding the consequences of fluctuations in power level, gas cleanup, etc., of an active gas discharge. The COS laser is unusual in that the terminal level of the laser transition can be populated by thermal excitation near room temperature. Therefore, we propose to stabilize a 10.6-,U CO, laser with respect t o a CO absorption line in a passive reference cell.

A frequency shift from line center can be sensed by the conversion of phase modula- tion of the laser output to amplitude modu- lation by passage through the absorption cell. This stabilization method is similar to one suggested by Siegman,Q* but utilizes a passive, thermally excited absorption cell rather than a discharge-excited cell t o pro- vide the reference.

Details of the system, with an analysis of limiting factors, are discussed, and pre- liminary results are presented.

Development Program.

to be published.

9 7 This work was sponsored by the NSF Science

88 A. E. Siegman, I E E E J. Qzlanfum Electronics,

7) Characteristics of COS-Xe-He LasersQ9 -P. 0. Clark and J . Y . Wada, Hughes Research Laboratories, Malibu, Calif. The replacement of X, by Xe in sealed-

off CO, lasers'00 has resulted in improved life with no sacrifice in power and efficiency. A small (50 cm by 1 cm), water-cooled, sealed-off Con-Xe-He laser with NaCl Brewster-angle windows was operated con- tinuously for 2800 hours. The test was termi- nated by damage to the Brewster angle win- dows, but at this time the output power was about 1 watt compared to a value of 6 watts which was the maximum power observed at any time during the test.

The power output from the COz-Xe-He laser is comparable to the C02-N2-He laser, while the efficiency is slightly higher. How- ever, the excitation mechanisms leading to such high power and efficiency are not im- mediately evident, contrary to the situation with the COz-N2-He laser. Double probe measurements reveal that the electron tem- perature of the COz-Xe-He discharge is lower than that characteristic of c02-N~- He. An excitation mechanism is hypothe-

Avionics Laboratory under Contract A F 33(615)- gQ This work was supported by the Air Force

5253. 100 R. Rempel and J. Goldsborough (private com-

munication) claimed higher sealed-off power output; they have since abandoned this line of investigation.

sized which involves efficient electron excita- tion of CO followed by collisional population of the upper laser level.

Further life tests and experiments to investigate the excitation mechanisms are presently underway.

SESSION 23-SOLID-STATE DEVICES VI : JUNCTION DEVICES (A) Chairman: D. Carley Organizer: J. J . Kleimack 1) Silicon-on-Sapphire Bipolar Transistorslo'

-F. P . Heiman and P . H . Robinson, R C A Laboratories, Princeton, N . J . All-epitaxial bipolar transistors have

been fabricated in silicon-on-sapphire films which exhibit a common-emitter low-fre- quency current gain hJe of 10 a t room tem- perature. The value of h,, increases approxi- mately as the square of the absolute tem- perature, which suggests recombination by charged Coulomb centers in the base region. Monotonic increase in h f a with collector cur- rent up to 100 mA (emitter area is 0 .8x1.2 sq. mils) is probably due to trap-filling in the base region. No conductivity modulation, which would result in beta fall-off, is seen up to 500 mA of collector current. This is a nar- row (0.6-pm), heavily doped (-10'' cm-3) base region.

High-frequency measurements indicate an f T of 350 MHz at 15 mA and extrapola- tion of a plot of 1/fT vs. l / I e yields a base transit time of 350 ps. Minority carrier life- time in the base region is measured to be 1 to 3 ns since h f , varies from about 3 to 10 with increasing collector current.

The silicon is deposited on single-crystal sapphire oriented in the [1102] direction which results in the growth of [loo]- oriented silicon. Arsenic and boron are used as the dopants in the n+-n-p-n+ structure. The total film thickness is approximately 7 ,~m and t he transistor structure contains a mesa-emitter and mesa-collector.

2) The Realization of a Ge-GaAs Hetero- junction Transistor with Usable Gain102- D. K. Jadus and D. L. Feucht, Carnegie- Mellon University, Pittsburgh, Pa. 4 Ge-GaAs wide band gap emitter

transistor has been realized that exhibits useable current gain. The method of fabrica- tion and the transistor characteristics will be described. Useable current gains of 15 to 30 are observed in a structure with an n-GaAs wide band gap emitter and a p-n Ge base- collector region at current densities of 1000 4/cm2. A typical device to be described has a collector doping of 1016/cm3, a l-micron- wide strongly graded diffused base with a maximum doping level of 5 X 101Q/cm3, and a

Army Research Office-Durham, and the 4ir Force

Research. Cambridge Research Laboratories, Office of Aerospace

102 This work was sponsored in part by the U. S