The current-voltage characteristic of n-type GaSb has been measured u p to 9 kV/cm at) 300 "K, and results for the longitndinal magnetoresistance a t 300 O K are given u p to 7 kV/cm. The experiments are compared with calculations based on a two-band model taking into account carrier transfer to higher valleys. Avalanche breakdown is observed a t the highest field strength under investigation.Die Strom-Spannungs-Charakteristik von n-Typ GaSb wurde bei 300 O K bis zii 9 kV/cm gemessen, der longitudinale Magnetowiderstand bis zu 7 kV/cm. Die Experimente werden mit Berechnungen verglichen, die auf einem Zwei-Band-Modell beruhen, wobei Ladungstrageriibergange zu hoheren Minima berucksichtigt werden. Bei den hochsten gemessenen Feldstiirken wurde ein Lawinendurchbruch beobachtet.The conduction band of GaSb consists of three sets of minima : The lowest one (r,) is located in the centre of the Brillouin zone, the second one (L,) consists of four spheroidal minima along the (1 11) directions in k-space lying about 0.09 to 0.1 eV [l] above the central minimum, and the third type (X,) of valleys is found a t the zone boundaries along the (100) directions, 0.315 eV [Z] above the central minimum. Due to the small separation between the first and the second minima both kinds are occupied by electrons in thermal equilibrium a t room temperature, and consequently contribute to the observed transport phenomena. By application of a strong electric field the electrons gain energy from the field and therefore the population of the L,-valleys should strongly increase. The XIminima will be only of minor influence for not too high field strengths, and will not be taken into account in the following treatment.To our knowledge no high electric field properties of GaSb have been reported so far. According to the calculations of Butcher and Fawcett [3] no negative differential conductivity will be obtained when the energy separation of the two sets of valleys under consideration is so low that appreciable population of the upper minimum will suppress the Gunn effect. A similar result may be expected for GaSb and Gunn effect has been reported only for Ga,Inl-,Sb alloys with 0.3 < z < 0.54 [4], where A is larger than 0.1 eV. However, the fact that carrier transfer does not cause a NDR in GaSb offers the so far unique possibility of studying the transfer mechanism without being faced with the ambiguity of interpreting experimental results in the presence of high field domains. I n this paper we want to report about the observation of current-voltage charaeteristics and magnetoresistance up to 9 kV/cm in GaSb and their interpretation in terms of a simple two-band model. _ _ l) Work supported by the "Fonds zur Forderung der wissenschaftlichen Forschung", Austria.
