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In this article, we review the recent progress on GaAs MOSFET's using in-situ MBE-grown Ga2O3(Gd2O3) as the gate dielectric. Both depletion-mode (D-mode) and inversion-mode (I-mode) GaAs MOSFET's with negligible drain current drift and hysteresis are demostrated. The absence of drain current drift and hysteresis indicates that the excellent stability of the oxide and low oxide/GaAs interface state density have been achieved. The drain current density and transconductance are about one order of magnitude higher than the best previous reported data in the literature for an inversion-mode GaAs MOSFET. Excellent high frequency and power performances were also measured from the depletion-mode devices. These improvements are attributed to the excellent Ga2O3(Ga2O3) oxide properties and novel processing techniques.

THE occupancy of air raid shelters presents, actually or potentially, many of the whole range of problems with which the practice of ventilation is concerned. The term ‘ventilation’ is here used to include heating and other air-treatment; it may be defined as ‘the provision of air hygienically and physiologically adequate in quantity and quality’. In air raid shelters conditions arise which tend to reduce the efficiency of ventilation very considerably. While on one hand, the supply of air is hampered in a number of ways by safety requirements, the demand tends at the same time to be greatly increased. Structural alterations to places used as air raid shelters usually require the blocking or baffling of the natural airways; lighting restrictions interfere further with ventilating arrangements; the danger of gas attack may reduce the available air supply merely to the air capacity of the shelter. The fitting of ventilating appliances may entail some structural weakening of a refuge; and the dependence of most large plants on outside power is also a potential source of weakness. Furthermore, since in shelters the ordinary density of living-room occupancy is much exceeded, satisfactory standards of ventilation are distinctly more difficult of attainment.

We demonstrate a vacuum lithography process which uses a finely focused Ga ion beam to write the pattern which is then transferred to the InP pattern by low energy dry etching. Surface steps on the order of 1000-2000A in height, and lateral resolution limited only by size of the ion beam, can be efficiently prepared using moderate Ga ion fluences. The surfaces prepared by this process are damage free and suitable for epitaxial overgrowth. GaInAs/InP heterostructures grown on in-situ patterned substrates show excellent morphology and high luminescence efficiency.

Recent progress of GaAs-on-Si technology is reviewed and the importance of initial nucleation is emphasized. Growth initiation with a Ga prelayer at a suitable low temperature combined with migration enhanced epitaxy and in-situ thermal annealing has a prospect of giving substantially improved material quality. During the initial growth, use of the minimum necessary As4/Ga flux ratio is found to be critical. The random alignment of the major axis of the oval defects is suggested to be an alternative simple technique to detect the presence of antiphase domains. Patterned growth or post growth patterning releases tensile stress only if the growth edges are free. GaAs-on-Si was completely relaxed from stress by post-growth patterning to 5 μm × 5 μm size patterns. Steps on the surface due to substrate misorientation do not affect the two dimensional electron gas (2DEG) transport properties in AlGaAs/GaAs selectively doped heterojunction transistor (SDHT) structures. For a sheet density of 1012 cm−2, the 2DEG mobility >50,000 cm2V−1s−1 at 77 K was obtained on Si substrates, which is sufficient for fabrication of high performance SDHTs. The study shows that GaAs-on-Si has a great potential for SDHT technology.

In optical experiments with laterally patterned modulation-doped GaAs/AlGaAs quantum wells we observe spatially separate confinement of electrons and holes to one-dimensional quantum wires. We determine the one-dimensional subband spacing and Fermi energy from inelastic light scattering and photoluminescence spectra. From these measurements we directly determine the one-dimensional electron density.

The biaxial tensile stress of 2.65 kbar in as-grown GaAs/Si for T < 100K is reduced by post-growth patterning of the GaAs and the reduction in stress, as determined by photoluminescence and cathodoluminescence, is dependent on the pattern size and shape. For stripe patterns less than 15 gm wide the stress is largely uniaxial with stress relief normal to the stripe direction. Rectangular patterns exhibited stress relief in orthogonal directions, and a 9 x 12 µm2 rectangle exhibited an average stress of 0.5 kbar. For as-grown GaAs/Si layers 0.9 to 3.25 µm thick, the stress is weakly dependent on layer thickness. For T > looK the stress in as-grown GaAs/Si is reduced and at 295K a value of 1.51 ± 0.21 kbar is obtained. With patterned growth, using a native SiO2 mask, no reduction in stress was observed irrespective of the pattern size, indicating the importance of free GaAs edges in obtaining stress relief.

Growth at Adolescence By Dr. J. M. Tanner. Pp. xii + 212. (Oxford: Blackwell Scientific Publications, 1955.) 32s. 6d.

SWEAT collected from normal male subjects carrying out work at high temperatures and humidities was analysed for chloride, lactic acid and urea. The osmotic pressure, as estimated by the freezing point in two hundred samples, is found to be accounted for by the osmotic pressure of these three constituents added together to the extent of about 95 per cent. Sodium chloride, on the average, accounts for about 80 per cent ; lactate accounts for about 11 per cent.

Genetics and the Races of Man An Introduction to Modern Physical Anthropology. By Prof. William C. Boyd. Pp. xvii + 453. (Oxford: Blackwell Scientific Publications, Ltd., 1950.) 30s. net.

THE subdivision of modern man into distinct species rather than into "races" is justified in the first instance, says Prof. R. Ruggles Gates in his new book, on the score of "convenience"(p. 11). "Consistency in nomenclature and methods of classification necessitate the recognition of several species of living man", he adds (p. 406). Like Prof. Kuggles Gates, anthropologists well appreciate the difficulty of distinguishing (except arbitrarily) clear cut races of mankind and of specifying the criteria by which they are to be recognized. Indeed, at the recent International Anthropological Congress at Brussels the complexity of the problem received fresh affirmation. One might have hoped then that the first-fruits of Ruggles Gates' advocacy of the "convenience and cogency"of human species would be that the latter would prove easier to detect than the conventionally recognized 'races' or variants. However, he does not appear ready yet to adjudicate on the taxonomic rank of the many more or less distinctive groups which he recognizes. (The elaboration and adornment of the charts on p. 56 and p. 161 illustrating these groups need not be taken too seriously.) Towards the end of the book (p. 388) he puts forward five strong claimants to the rank of species in the Caucasian, Mongolian, Australian, Negroid and Bushman stocks ; but he does not, unfortunately, justify this selection by any detailed reference to the taxonomic and phylogenetic criteria which he insists are at hand to establish species differences ; nor is it made plain in which way these particular 'species' exemplify "consistency in nomenclature and methods of classification". Indeed,-it comes rather as an anticlimax to find, near,the end of the work (p. 378), that for the conferment of species rank one may have, after all, to fall back on the "opinions of a competent systematist". Human Ancestry from a Genetical Point of View By Professor R. Ruggles Gates. Pp. xvi+422+27 plates. (Cambridge, Mass.: Harvard University Press; London: Oxford University Press, 1948.) 42s. net.

IN the report1 on the main results of our re-examination of the Piltdown material, we gave reasons for regarding the chromate staining of the mandible as indicating a deliberate attempt to match a modern bone with the mineralized cranial fragments. The actual composition of this bone (3.9 per cent nitrogen, less than 0.03 per cent fluorine) suffices to prove its modernity; but the chromate staining, combined with the artificially abraded appearance of the molars, indicates that it is not only modern but also fraudulent.

THE recent University of the Witwatersrand-Nuffield expedition to the Kalahari desert enabled one of us (J.S.W.) to collect blood samples from Naron Bushmen, living their traditional hunting life and from Bushmen employed on farms in the vicinity of Ghanzi, Bechuanaland. The blood-grouping results on these specimens have already been reported1. In addition, two of us (R.S. and J.S.W.) were able to obtain samples from Hottentot (Nama-speaking) subjects in the Richtersveld area of Little Namaqualand and from Cape-coloured people in the Springbok and Steinkopf regions. Since the genetical variants of the serum proteins have not previously been studied in these peoples the sera were forwarded to London by Dr. A. Zoutendyk, who also kindly provided a series of Zulu sera, collected in Johannesburg, for comparison. The sera were examined by starch-gel electrophoresis using B.D.H. potato starch hydrolysed by the by the method of Smithies2. The discontinuous buffer system described by Poulik3 was used in routine screening. After addition of haemoglobin to saturate the hatoglobins the sera were inserted into a wide gel on pieces of filter-paper in batches of twelve. One half of the gel was stained with amidoschwartz and the other was treated with benzidine-hydrogen peroxide reagent. Specimens in which haptoglobins were weak or apparently absent were also run by the vertical method4 and this was also used to compare β-globulin variants the identity of which as iron-binding transferrins was checked with the nitroso-R reagent of Smithies5. The results are shown in Table 1.

Anthropogenesis A Study of the Origin of Man. By Prof. Ant. Pannekoek. Pp. 120. (Amsterdam: North-Holland Publishing Company, 1953.) 12s.

Origins of Man: Physical Anthropology By John Beuttner-Janusch. Pp xxvii+674. (New York and London: John Wiley and Sons, Ltd., 1966.) 72s.